Manual For Rural Water Supply

A project of Voluntesrs in Asia

by:

Swies Ca?ter for Appropriate Technology

Published

by:

Swiss Center for Appropriate Technology

Varnbuelstraese 14

CH-9000 St. Gall

Switzerland

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Available from:

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WITH MANY DETAILED CONSTRUCTIONAL SCALE -DRAWINGS

Publication No. 8

St.Gall 1980

Varnbgelstr 14

CH-9000 St .Gallen

Tel. 071 I 23 34 81

MAT

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Angepamte

T@hnik

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SKAT SKAT

SWISS Center for Centre Suisse pour la

Appropriate Technology Technologle ApproprMe

at the lnrtltute Iw Lstln-American

a I’lnstltut Latino-Ambricain

Research and for Development

et de Coop4ration

au

DBveloppe-

Cooperstlon, St.Gall University

ment, Unlversitb de St-Gall

SKAT

Centro Suizo para

TAcnologla Apropiada

en el lnstituto Latinoamericano

y de Cooperacih Tknica,

Universidad de Sankt-Gallen

MANUAL FOR

WATER SUPP

WITH MANY DETAILED CONSTRUCTIONAL SCALE .-DRAWINGS

Publication No. 8

St.Gail 1980

Edited and

compiled by:

Cover photo:

Published by:

Comments,

enquiries:

Copyright:

Price:

Helvetas, Swiss Association for Technical

Assistance, Zurich, Switzerland and Yaounde,

Cameroon

HELVETAS

SKAT, Swiss Center for Appropriate Technology

at the Institute for Latin-American Research

and for Development Cooperation, St. Gall

University

All questions and commeri'ts concerning this

publication and its contents are welcome at

SKAT. Please use the postcard-questionnaire

enclosed.

Material of this publication may be freely

quoted, translated or otherwise used.

Acknowledgement is requested.

SFr.

34.--

Preface by the Editor

Helvetas (SATA! and the Community Development Department of the United

Republic of Cameroon (CD) have been closely working together since 1964.

The purpose of this cooperation is to support the effort of the rural

population to build up a local infrastructure by giving technical assistance.

All these community development activities are self-help projects, initiated

by the local people. Priority is given to the most deprived areas.

Water evidently plays a very important role in the development of rural areas.

A supply of clean drinking water not only reduces the numerous diseases caused

and transmitted by polluted water, but is very often the first step towards

other development scopes like health, nutrition, sanitary programmes, etc.

When a water supply is being planned, all technical and socio-economical

aspects have to be considered carefully. As one of the consequences simple

techniques, simple designs, and a simple system are used. In this context

greatest attention has to be paid to the fundamental problem of maintenance,

that is even before starting with the construction of a project.

Assisting the rural areas and their population in im+:oving the quality and

accessibility of drinking water is one of the major concerns of the Community

Development Department in Cameroon. During all these years of collaboration

the technical staff of CD/Helvetas has gained valuable experience in the

planning and execution of rural water supply and water point projects. Intending

to provide Community Development officials, engineers and field staff who arc

planning and implementing water schemes in rural areas with useful information,

a Manual for Rural Water Supply was first issued in 1975 (SATA-Helvetas Buea,

Cameroon). Since then, improved and more adapted techniques and material have

been developed which lead to this revised second edition of the Manual for

Rural Water Supply. The technical data and drawings needed for the Manual

have been compiled by the CD/Helvetas field engineers in Cameroon and partly

completed by referring to various international publications.

We

hope that this Manual will serve its purpose by contributing to a general

improvement of the water conditions in developing countries.

I

Our sincere thanks go to all persons who have been involved in the preparation

of this Manual.

May 1980

HELVETAS

Swiss Associa'tion

for

Technical Assistance

St. Moritzstrasse 15

8042 Zurich / Switzerland

HELVETAS

Swiss Association

for Technical Assistance (SATA)

P.O. Box 279

Yaounde / U.R. Cameroon

Foreword by the Publisher

It is very fitting at the beginning of the UN decade dedicated to water that

an organization that has got a vast experience in rural water supply

construction in developing countries should decide to make a special effort

and compile and edit material of field engineers to make tv,e publication of

a comprehensive practical manual on this subject possible.

The result of this effort is the manual presented here. It is based on actual

field activities during the last fifteen years in the United Republic of

Cameroon (West Africa). Despite its being based on experience in one specific

country the material is certainly very useful in the context of other countries

also and provides a guide line on how to identify, plan, organize and execute

drinking water projects.

Manyfold aspects such as hydrology, safety standards for drinking water,

design of water schemes, construction and maintenance, spring catchments,

barrage and river intake systems, distribution systems and water lifting are

treated. The material is suitable specially for ::ngineers and construction

supervisors but serves also to give a comprehensive overview of all aspects

of rural water supply to non-technical people.

The technology that has evolved and that is documented in this manual is

first class craftmanship using traditional western techniques and materials.

Emphasis is on solid, longlasting structures of simple design and on the use

of labour intensive methods and local materials wherever possible. The goal is

to achieve systems of trouble free operation, stable quality of drinking water

and minimal,simple maintenance and management requirements.

The field of well digging is covered very briefly only, and the exploitation of

alternative energies for water lifting is referred to only in connection with

the use of hydraulic rams. Specific alternative technologies such as alternative

cements, the use of bamboo and other local material for reinforcement and

traditional, local construction skills are net included since the manual is

based on action oriented projects rather than research.

Although the publication is based on actual field experience and presents

practical examples, it is not presumed to be either exhaustive or final. It is

certain that local adaption and modifications will always be necessary. With

this publication, SKAT intends to create an opportunity for field testing and

feedback of information. The reader therefore i., requested to give his comments

and suggestions for changes, corrections and additions which he considers

necessary or useful. Such contributions will be gratefully accepted by SKAT and

will

be used in the future revision of the manual.

It would not have been possible for SKAT to publish the manual without the help

of Helvetas who not only compiled and edited all the material but also sponsored

the publication. It is therefore only appropriate that we express our thanks to

Helvetas and to all the people who contributed to this work.

St. Gall, May 1980 ,

SKAT, Swiss Center for

Appropriate Technology

TABLE OF CONTENTS - SUMMARY

..-m__

1. HYDROLOGY

l-l Definition and hydrologic cycle

l-2 Climatic pattern and rainfall

1-3 Run-off and infiltration

l-4 Drainage in Cameroon

5

6

13

14

2. CHARACTERISTICS OF WATER

2-l Water sources

2-2 Standards for drinking water

2-3 Aggressivity of water towards building material

2-4 Prevention of corrosion

15

17

19

22

2G

3. INVESTIGATIONS AND BASIC DATA FOR RURAL WATER SUPPLIES

3-l General fieldwork

3-2 Specific consumption

3-3 Location cf water source

3-4 Measuring of water quantities

3-5 Analysis of water

31

33

34

35

40

4. DESIGN AND CONSTRUCTION OF RURAL WATER SUPPLIES 45

4-l General lay-out 49

4-2 Wells 55

4-3 Spring catchment 65

4-4 Water point 78

4-5 Barrage and river intake 80

4-6 Water treatment 83

4-7 Storage 99

4-S Distribution system 103

4-9 Water lifting 139

5. ADMINISTRATION OF PROJECTS

5-l Technical report

5-2 Execution of project

5-3 Completed project

151

153

156

8. INDEX OF KEY WORDS

6. MAINTENANCE OF RURAL WATER SUPPLIES

6-l Maintenance general

6-2 Maintenance instructions

7. SELECTED BIBLIOGRAPHY

Appendix:

NORM

PLANS AND SCHEME PLANS

(Constructional Scale Drawings)

1

159

161

167

169

Chapter 1: HYDROLOGY

Table of contents page

l-l

1-2

1 - 2.1

1 - 2.2

1 - 2.3

1 - 2.4

1-3

1-4 DRAINAGE IN CAMEROON

DEFINITION AND HYDROLOGIC CYCLE

CLIMATIC PATTERN AND RAINFALL 6

Quantity of rainfall 6

Variation of rainfall 6

Tables of monthly rainfall 11

Intensity of rainfall 12

RUN-OFF AND INFILTRATION ,

3

5

13

14

l-l DEFINITION AND HYDPOLOGIC CYCLE

Hydrology is the science of distribution and behaviour of water in nature.

Hydrology is a part of climatology. The cycle of water

or

Hydrologic Cycle

is without beginning or end and consists of the following:

- Precipitation: All water from the atmosphere deposited on the surface

of the earth as either rain, snow, hail or dew.

- Surface run off: The water which is derived directly from precipitation

and passes

over-ground

into water-courses is known as surface run off.

The surface run off then consists of the precipitation less the losses

from infiltration and evaporation. '.

- Evaporation, transpiration: Combined loss of water from land and water-

surfaces by evaporation and plant transpiratjon.

- Percolation; The term percolation describes the passage of water into,

through and out of the ground. The term infiltra;.ioll is frequently used

to describe the entrance of water into the grclane ant: its vertical move-

ment down to the ground-water table, while percola?ion LP ground-water

flow is applied to the movement of water after i+-

kss

reached the water-

table.

Fig. 1 Hydrologic Cycle

l-2 CLIMATICPATTERWAND RAINFALL /

The main features of the climate in Cameroon are the 4 - 5 months-long dry ;

season from November to March and the corresponding rainy season of 7 - 8 /

months. I

Notes on the climatic characteristics of the various areas are based on I

inadequate records in terms of duration and number of stations. Neverthe-

less, an idea of the main climatic zones can be found when considering

some basic factors:

- Throughout most of West Africa, the rainfall and the humidity decrease '

with increasing distance from the coast, but in South-West and North-

West Province of Cameroon this pattern is sharply modified by the

topography.

- The main rain-bearing winds come from the south-west. Wherever these are

interrupted by high land, heavy precipitations result over all south-wes

facing slopes with complementary rain shadows in the N.E. For example,

Dibundcha on the south-west side of Mount Cameroon averages 10.4 m of

rain per annum, whereas Mpundu at the northern side receives only

1.5 m per annum. Similarly Fontem, at the south-west of the high plateau1

averages 4.3 m compared to Ndop with 1.6 m per annum. I

1-2.1 QUANTITY OF RAINFALL

Rainfail quantities can be mapped with isohyets, i.e. all points with the

same annual rainfal1 are linked and the resulting lines give us an idea

of the distribution of the rainfall in a region. (see Fig. 2 and 3!

l-2.2 VAFKIATION OF RAINFALL

The rainfall varies greatly throughout the year and from one year to the

other as well as from one station to another (see annual rainfall map).

The monthly variations have been analysed by Brown and Clarkson for the

Bamenda Station records 1923 - 1953 and the results are shown in Fig. 6.

In the diagram, the upper and the lower ends of the monthly pillar show

the greatest and least rainfall recorded during this period. In four out

of five years the monthly rainfall may be expected within the dotted

lines. The black line across indicates the arithmetic means of 30 years

of records.

6

,m

Fig. 2 _Isohyetes West-Coast (1967)

Fig. 3 Distribution of annual rainfall

1 OVER 375

cm

2 200 - 375

cm

3 SO - 200

cm

4

100

-1SOcm

I 700--tOOem

6 BELOW

70

cm

. .

. . . ,

..*...

. . ..a..

A

. . . . .

. l .

. l

6

!s

IT FouRtAU

70 am

. -

l . ‘**: .

l ‘* . *

. .

---I

. . * .

’ . .

FiG.('$ Bnd 5 Monthly rainfall

.,. . . ..i

-3 ,., ,<l

_, .~

.,.. .“. . .

_

’ I

. . . . . .

,: %

I

a

:: ,: .\.

). ,* n Iv

I ” I

),, ’ UluJ

Nl llV3NIVtl

Fig.

6 Monthly variation of rainfall at Bamenda Station 1923-1953

mm.

000 ’

600

t 1

MAX.in 30

1 in 4

MEAN

3 ih 4

MIN in 30

--me --me

-r -r -C- -C-

m-w. m-w.

-- M-w -- M-w

----I

v

14

161

D 1970

f

544

3u0 354 470 m 77

608 605 510

173 142

1 576 249 536 754 453 261 90

4U2 337 630 487 264 6

312 591 332

6442 151 116

660 419 529 492 104

340 405 460 457 2u9 1;

4u6 369 4u5 390 20 22

667 103 563 760 ma 79

530 726 564 441 40 -

304 557 576 141 34

532 502 400 77 53

U9

U6 494

560 223

45 133

total

3246

4401

cz2

;z

3422

22

3552

hw much rein falls within a certain

ta for the calculations involved in

rvation mrthworks.

1-3 RUN-OFF AND INFILTRATION

The quantity

of

water running from an area into streams and finally to

the sea is not the same as the rainfall.

The rainfall is equal to the total o?:

- direct evaporation

- transpiration through vegetation

- infiltration

- run-off

The whole run-off and part

of

the infiltration supply the streams. Rockv

areas provide flood and low water directly according to the rains.

Lateritic or other porous, water-holding soils supply the streams with

underground-water.

Infiltrated water form the ground-water and through its natural filtration

it can be

used

directly

as drinking water (so long aa protective measures

for

catchmente are adopted and the thickness

of

the stratum which

covers

the water-bearing soil is big enough).

The charaizteristics of the yield

of

a spring depend on the type of soil

and

subsoil. In

rocky

areas the

quantity

of

water

will directly depend

upon the rainfall. Surface springs will also dry up shortly after the rainy

season and supply again after the firs* rains.

Springs

from

deep lateritic covers or from far distant catchment areas are

more regular

but

their lowest supply quantity does not coincide with the

lowest rainfall.

1-4 DRAINAGE IN CAMEROON

The principal watershed of Cameroon begins in the Rumpi Mountains north

of Kumba and continues through Kupe, Manenguba, Bambutu, Bamenda Banyo

and Ngaoundere to Ubangi-Shari across the frontier. It is the main source

of

the country's rivers , which flow in four main directions: north into

Lake Chad, north-west into River Benue (Niger), south-west into Gulf of

Guinea and south-east into Kadei, a tributary of River Congo. These

correspond nearly to the five main drainage basins: Chad Basin, Benue

Basin (Niger), Sanaga Basin,

(see

Fig.

9) Congo Basin and Basin of Coast Rivers.

Fig, 9 Drai,nage in Camerpon

lhlcrchrd

2 tugar

3 cops0

4 ram

5

coMt

Bivora

Chapter 2: CHARACTERISTICS OF WATER

2-l

2 - 1.1

2 - 1.2

2 - 1.3

WATER SOURCES

Ground water

Springs

Streams

2-2

2 - 2.1

STANDARDS FOR DRINKING WATER

International standards

2-2.1.1 General remarks

2-2.1.2 Bacteriological standards

2-2.1.3 Chemical standards

2'- 2.2

Standards for drinking water in Cameroon

2-3

2 - 3.1

2 - 3.2

2 - 3.3

2 - 3.4

2 - 3.5

AGGRESSIVITY OF WATER TOWARDS BUILDING MATERIAL

General

PH - value

Carbon dioxide (CO21

Hardness

Other influences

2-4

2 - 4.1

2 - 4.2

PREVENTION OF CORROSION

General

Cement products

2-4.2.1 Concentration limits

2-4.2.2 Prevention of destruction

2-4.2.3 Asbestos

cement pipes

2 - 4.3

2 - 4.4

2 - 4.5

Galvanized steel pipes

2-4.3.1 Concentration limits

2-4.3.2 Prevention of corrosion

Plastic pipes

Examples of practical application

Table of contents pagP

17

18

19

20

21

22

23

25

26

27

28

29

15

2-1 WATER-SOURCES

2-1.1 GROUND-WATER

Ground-water is water which by percolating through the ground reaches

the ground-water table. The quality of the ground-water depends on:

- The thickness of the stratum which covers the water-bearing soil.

This is important because of indirect contamination like latrines,

fertilizers etc.

- The porosity of the subsoil which influences the natural filtration

process.

The quantity of ground-water depends on:

- The intake area: It is important to realize that the topographical

basin does not necessarily correspond with the geological or hydro-

logical drainage area.

- Annual rainfall percolation: This depends on the nature of the inta! r

area, e.g. kind of vegetation (forest, farm, bush)

- Perviousness of the ground: This depends on the kind of material,

stratification and its homogeneity.

- Storage capability of the ground: This depends on the same factors

as perviousness and the intake area.

2-1.2 SPRINGS

If ground-water leaves the ground without artificial help we call it

spring-water.

Spring-water is usually the best water quality. Whenever a water-point

or water supply is planned, we investigate first if there is a

possibility of using a spring. The quality and quantity which can be

obtained depend on:

- Intake area: It is important to realise that the topographical basin

does not necessarily correspond with the geological or the hydrological

drainage area.

- Annual rainfall percolation: This depends on the nature of the intake

area, e.g. kind of vegetation (forest, farm, bush).

- Continuous flow: The following points influence the continuous flow of

a spring: - thickness of the stratum which covers the water-bearing soil

- perviousness of the ground

- storage capability of the ground

Therefore we know t. Jxtremes:

Case 1: -A thin s atum covers the water-bearing soil.

- The sat- ated stratum has a great perviousness (e.g. cracks

and fissures).

- The water-bearing soil has little storage capability (few

pores

which could fill with water).

case 2: -

A

thick stratum covers the water-bearing soil.

- The saturated stratum has a small perviousness.

- The water-bearing soil has a big storage capability.

In case 1 a single rainfall influences the flow volume of the spring.

In case 2 only the annual rainfall will influence the flow volume of

the i :>ring (continuous flow).

Fig. SPRINGS

2-1.3 STREAMS

,-

ARTESIAN

SPRINGS

The run-off or stream-flow is the water which is gathered into rivulets,

SPRING -1

NWL a ~I&CRW#W~~R PCRC~ATC

INTO

LWL = GAOlJM WaTLR fLows INTO TM

RIVER (INVISIU SPRINGS)

brooks and rivers. The volume and variation of run-off are influenced

chiefly by the rainfall and its distribution by the size, shape, cover

and general topography of the catchment area and by the nature and

condition of the qround,

2-2

STANDARDS FOR DRINKING-WATER

-

2-2.1

INTERNATIONAL STANDARDS

2-2.1.1

GENERAL

RRMARKS

Water intended for human consumption must always be free from any

substances which provide a hazard to health. Supplies of drinking-water

should not only be safe and free from dangers to health, but should also

be as aesthetically attractive as possible. The location, construction,

operation and supervision of a water supply - its sources, reservoirs,

treatment and distribution - must exclude all potential sources of

pollution and contamination.

The problems of defining standards of quality for safe and acceptable

water supplies have

been

studied by experts concerned with matters of

water sanitation. The World Health Organization (WHO) has studied these

problems to offer technical guidance for health and sanitation

administrations to tighten or revise their regulations on water-quality

control.

2-2.1.2 HACTERIOLOGICAL STANDARDS

Water circulating in the distribution system , whether treated or not,

should not contain any organisms which may be of faecal origin. The

presence of the coliform group should be considered as indication of

recent or remote faecal pollution.

A standard demanding the absence of coliform organisms from each 100 ml

sample taken from water entering the distribution system - whether the

water be disinfected or naturally pure - and from at least 90% of the

samples taken from the distribution system , can be applied in many parts

of the world, Although there is no doubt that this is a standard that

should be aimed at everywhere, there are many areas in which the

attainment of such a high standard is not economically or technically

practicable. In such circumstances there would appear to be economical

and technical reasons for establishing different bacteriological standards

for public water supplies with treated or disinfected water and for those

with untreated water. The following bacteriological standards are re-

commended for treated and untreated drinking-water

for

present use

throughout the world.

Coliform density is estimated in terms of the "most probable number" in

100 ml of water, called "MPN" Index.

To get the coliform bacterial count (MPN Index) of the water, the Millipore

Laboratory can be used (see chapter 3-5.1).

sted Water (by chemicals1

ia shall not be

detected or the MPN index of coliform micro-organisms shall be less than 1.

None Of the samples shall have an MPN index of &lifarm bacteria in excess

of 19.

19

c

An HPN index of 8 - 10 should not occur in consecutive samples.

When the microfilter c hnique is used, the arithmetic mean of numbers of

coliform

group organids shall he less than 1 per 100 ml, and shall not

exceed 4

per

100 ml either in any two consecutive samples or in mDre than

10 % of the samples examined.

Cheamical treatment of water (e.g. chlorination) has not been applied in

CD/SATA-Nelvetas projects in Cameroon , mainly because of uncertainty

of

a

continuous rupply of the products.

b) Untreated water (incl. slow sand filter without chlorination)

Very often communal drinking-water is not chlorinated or otherwise

dieinfected

before

being distributed. In such water schemes the following

etand

- in 90%

of

the samplera examined in any year, the MPN index of coliform

microcorganisms should be less than 10. None of the samples should show

an MPN index

graater

than 20.

- if the MPN index is consistently 20 or greater , application of

treatment

to the water supply should be considered.

_ when the micro-filter technique is used in examination of water, the

arithmetic mean of the numbers of coliform group bacteria determined

shall be less than 10 per 100 ml, and shall not exceed 20 per 100 ml in

two consecutive samples or in

nmre

than lo& of the samples examined.

This standard is applicable

for

all the CD-SATA-Helvetas water supplies.

2-2.1.3 CHEMICAL STANDARDS

Chemical analysis plays an important role in the investigation of water

supplies and water quality. Attention is largely directed to the detection

and estimation of certain toxic chemical substances which may affect health.

a) Toxic substances

There are certain substances which, if present in supplies of drinking-

water and at concentrations above certain levels, may give rise to actual

danger to health.

A

list of such substances and of the levels of

concentration which should not be exceeded in communal drinking-water

supplies is given below:

Substance Maximum allowable

concentrations in mg/l

Lead 0.05

Arsenic 0.05

Bel.enam 0 ,Ol

Chromium 0.05

Cyanide 0.2

Cadmium 0.01

6axium 1.0

20

These substances cannot be analysed by simple field tests. Samples of

the chosen water source should be sent to a laboratory for specific

analyeis, @specially if the local population calls the water harmful.

(see chapter 34.2)

b) Chemical substances affecting the potability of water

The following criteria

are

important in assessing the ootability of water.

In view of the wide variations in the chemical analyses of water from

different parts

of

the world , rigid standards of chemical quality cannot

be established. The limits thereafter designated "acceptable" apply to a

water

quality which would be generally acceptable to consumers8 values

greater than listed as "allowable" would markedly impair the potability

of the water.

These limiting concentrations are indicative only and can be disregarded

in specific instances.

Substance

Total solids

Iron (Fe)

Magnesium (Mg)

Wanganeee (Wn)

Copper (C-u)

Zinc (Zn)

Calcium (Cal

Sulphate (So)

Chloride (Cl)

Wagn. and Sodium Sulphate

Phenolic

substances

Carbon Chloroform extract

Alkyl Benzyl Sulphonates

pH Range *

max. acceptable

IIHX.

all0wabl.e

concentration concentration

500 mg/l 1500 mg/l

0.3 mg/l 1.0 mg/l

50 " 150 I,

0.1 W 0.5 In

1.0 W 1.5 W

5.0 lo 15 "

75 II 200 II

200 II 400 w

200 II 600 I,

500 ,s 1000 I,

0.001 lU 0.002 w

0.2 )) 0.5 w

0.5 @a 1.0 ((

7.0 - 8.5 w less than 6.5

or

greater than 9.2

*This item can be analysed by field tests, the

others

can

be

found

out only in a laboratory (see chapter 3-5.2)

2-2.2

-S FOR DRIWKIWG-WATER IN CAMEROON 1

The standards of Cameroon correspond with the standards of France which ?

are laid down in article 1 of the Decree of 10th August, 1961 of the

i

~

;

"Conseil

HupBrieur

d'hygiine publique" and the decrees of 28th February,

1962

and

7th

September, 1967.

There correspond mite

or

less with international standards.

21

2-3

AGGRBSSIVITY OF WATER ON BUILDING MATERIAL

2-3.1 GENERAL

The aggressivity of

water

plays a

very

large role in a water supply.

Corrosion caused by the aggressivity of water means not only loss of

building-material

but

in addition reduction of the water quality

technically and hygienically. Especially endangered are those parts

of

a water scheme which are invisible like underground pipes, the

exterior of covered constructions etc.

The aggressivity of water is mainly determined

by its

pH-value. In

addition the free carbon dioxide plays an important role. Whether

*these two values prove aggressive or not depends much on the

carbonate hardness ot the water. That is why these three magnitudes

are described more in detail below,

2-3.2

PH - VALUE

The pH-value is very important in water technology. It indicates how

acid or alkaline (basic) a water sample is. It is the measure of H+-ions

(hydrogen ions) dissociated in one liter of water (the pH-value is the

negative logarithm of H+-ions concentration). One litre of pure and

neutral (neither acid nor basic) water contains an equal amount of

Ii+-itins and OH--ions (hydroxyl ions) , at a temperature of 22O a

concentration of 10s7 H-ions and 10-7 OH-ions = pH-value of 7. In acid

water the H-ions are overwhelming the OH-ions and accordingly the

pH-value is below 7. In alkaline water it is the opposite and the

pH-value is above 7.

In practice this neutral point of pH-value = 7 varies with the content

of calcium salt (hardness, see chapter

2-3.4).

For instance water of

pH-values exceeding 7 can also be aggressive if its calium salt content

is

very

low (see Fig. 11).

,

Fig. 11 PH-value for neutral watk- depending

on the

calcium

salt content

8,8

w

8,4

8,2

8,O

%7,8

T76

’ 7:4

E7,2

7,O

d-’ ! ’ ! ’ ! ! ! ’ ! ’ !H ! ’ 1

0 20 &I 60 Bo loo 120

140 160

fixed carbon dioxide mg/l

0 2 4 6 8 10 12 14 16 18 20

C.r.‘.‘.‘.‘-‘.‘-‘.‘.1

carbonate hardness

DG’

I

2-3.3 CARBON DI@JXDfI

Summary :

Only part of the carbon dioxide in water (the excess CO21 is aggressive

towards cement and iron products. The theory on this page shows the

con-

text, The figures 13 and 14 show the practical application (compare with

examples of chap,ter 2-4.5).

CO-J: Carbon dioxide in water

A \

Freee

carbon dioxide Fixed carbon dioxide

/ ------.

Associated CO2 Fully fixed CO2 Half fixed CO2

(harmless to CaC03

in (e.g.

Ca (HC03) 2

concrete! carbonates) in hydrogen

not

aggressive carbonates 1

not aggressive

total excess Partial excess

(prevents formation (lime aggressive,

of anti rust layer) attacks

concrete)

Free and fixed carbon dioxide (CO21 is found in

every

natural water.

Surface water generally contains much less free carbon dioxide than

ground water.

The fully fixed carbon dioxide is combined with calcium or magnesium.

Therefore its amount can be calculated according to the carbonate

hardness: ODG

l

7,f35 = mg/l of fixed carbon dioxide.

The half fixed carbon dioxide is combined with bicarbonates or hydrogen

carbonates. Its amount is equal to the one of fully fixed CO2.

Part of the free carbon dioxide, the associated CO2, is necessary to

maintain the calcium hydrogen

carbonates

in solution. Therefore the

associated CO2 is depending on the carbonate hardness (see Fig. 12).

Fig. 12

The associated

carbon dioxide

0

d

2il EiO 100 W 140 160

fixed CO2 mgll

0 2 4 6 8 10 I2 11 I6y120

I - I . I . I _ I . ‘ a - 1 . I . J

carbonate hardness DG *

The part of free carbon

dioxide exceeding the

associated CO2 is the

excess CO2.The excess carbon

dioxide is able to attack and

dissolve the metallic materia

as well as the calcium carbo-

nate in mortar or concrete.

Small amounts of calcium

hydrogen carbonate,

corresponding to a hardness

of less than 2O DG, do not

require any associated CO2,

The total free carbon dioxide

of soft water is thus

aggressive (compare

Fig. 13

and 14).

Fig. f3

~ggressivfty

towards cement products

(concrete,

mortar,

AC-pipes) depmding on the DG and the free CO2

0 2 4 6 8 10 12 14 16 18 '20 22

carbonate hardness ” DG

Fig.

14 Aggressivity towards iron products (steel pipes) depending

on the DG and the free CO2

0 0 2 4 6 8 Dl2l416182022

Carbonate hardness @DG

24

The hardness of water is dictated by its content of calcium and magnesium

salts, Water containing much calcium ano magnesium is termed hard, that

containing little, soft, This is expressed numerically by the degree of

hardness. Unfortunately there is no international unit established so far.

Degree of hardness - conversion modulus:

1 grain CaCOJ/gallon = 17,l mg CaC03/1 = 0,96ODG

10 mg CaO / liter = 1 German degree of hardness (ODG)

10 mg CaC03/0,7 liter = 1 English degree of hardness

10 mg CaC03/ liter = 1 French degree of hardness

10 DG = 1,25 English degree of hardness

lo DG = 1,78 French degree of hardness

Degree of hardness

OlG

o- 4

4- 8

8 - 12

12 - 18

18 - 30

over 30

This water is termed as

very soft

soft

medium hard

considerably hard

hard

very

hard

Three different kinds of hardness are distinguished:

- Total hardness

In natural w'ater, calcium and magnesium are largely combined with carbon

dioxide, namely as hydrogen carbonate. Usually a small amount is

combined also as sulphate, chloride, nitrate, silicate and phosphate.

The sum of all these calcium and magnesium compounds yields the total

hardness.

- Carbonate hardness

This includes only the part of calcium and magnesium which is combined

with carbon dioxide. When water is boiled for a longer period, the

calcium and magnesium combined with carbon dioxide are almost entirely

precipitated as insoluble carbonates. One refers thus to a temporary

or transient hardness,

now

generally spoken of as carbonate hardness.

-

Non

carbonate hardness

The fraction of the calcium and magnesium remaining in solution as

5 sulphate, chloride and nitrate after boiling constitutes the residual

hardness, formerly also referred to as permanent or mineral acid hardness.

Wow this is more accurately termed non carbonate hardness.

2-3.5 OTHER IWFLYEWCES

Concentrations above certain limits of sulphate (*3Omg/l) or sulphite,

chloride@100 mg/l), humic acid etc. can also be very aggressive towards

building materiels.

m

describe all

these influences

in detail is beyond the framework of this

book, Moreover such detailed analyses require a very well *equiped laboratory.

25

24.2

Cement, mortar, concrete, aslmstas cemant pipe conbin calcim carbn&te

vhich dissolves in contact with sggre

2-4.2.1

- Acid v&tar @I v&u@ kmlow ths neutral 1 , Pig, 11.) must kr regrrdd

am h88rmfui to concrete, It hamu* rmful if the pH value is more

than 1 to 2 point

blow

thf3

neutral line.

-

AS

it can be seen from Fig. 13,

soft

water (with IOU carbnate hardness)

becumes always very aggressive

if

it contains free

aclgresoive

CO2

dissolves the calcium salts

of

the

ic dastroys gradually theBe cement product

very rapidly.

carbon dioxide. This

concrete and mortar and

ng water with such

cr Alkmlim watw (Fig. 11, line) can ill~ilo CBUP~ d

Qnt &x’oducto if

the above 300 mq/l in

satanding

mg/l in flowing wif magnesium

5ulphates

and, tc3 zi

~11 %xtrPnt also the corresponding chloride , dsetroy concrete,

-

Ham%ul

to concrete is als~s wetlsr containing hydrogen sulphide and larger

alfum salt5 (@ .g. wa

- cuncrQt;8 is ttackQd

by vat r containing ~~Iium hydrogen carbonate

( idly in ceartal arsPrs1.

26

nt than porous concrete.

t pus”Lbla water-

t E*ternd such as

spetrion), plastic

occuxfng wkth &SW

27

It the o%yfpn

content

im OXUW~IVI, not in genuinely

diouolved

form

bilky W&ld&ty of wtex), iron irr likmhe

attacked.

- Iron im elbmym attmkad and bimsohd ky water

containing ~ree8tv.e

uhich preventa thm forution of a

protective layer against

ena Pig. 14)

l

- I&

&B-value

@hould altray be equal to or juot

below the equilibrium for

unprotected iron piparr -Cl,5 point* for gelvanieed

steel pipes (see Fig. 11)

- Unp+akcted iron pipem ere

attacked by

hydrogen mulphlde (e.g. in B-soilr

- Wnt8r with a high chloride eontmt (e.g. brackish vater)

attacks iron pipe6

rtmmgly. The

Limit

for

unprotected iron pipes icr

L5Omg/Liter in aoft

water,

- sp+cibl rttention bar to bm given to the e&mnal attack.

- Steel pipes ue mre twuceptib~e to chemlcrrl attacks than cast iron

pipes.

bet

&ton

pipee ue more reeirrtant than steel pipes against

soft water

of

high oxygen eontent and aggremive properties.

24.3.2

Ptevuntbn

of

corro8ion *

- llrdwtion of the recrreroive crcbn dioridsr

re

chapter 2-4.2.2.

- &on piper have to be coated by relted bit-n of

coal4.ar

pitch (eo-

c?ailatd *@ynapLmt~~in GIW of ewtawnal

amm3eelvity (e.g. in acid peaty

m&l@, lou

end

clay

~4th little calc$un and in salty ground water etc.1 .

28

2-4.4 PMSTIC PIPES

Plastic pipes are either of PVC (polyvinyl chloride) or of PE (polyethylene)

(see chapter 4-8.2.31.

Since 1959 the fabrication of plastic pipes has been adapted more and more

to

the

claims of water engineering.

Plastic pipes have the advantage of not beeing attacked

by

any aggressive water

They suffer

no

destruction

from carbon

dioxide, humic acids, sulphates and -

chlorides of any concentration in tapped water or soil. They have smooth walls

and no incrustations. That is why plastic pipes are applied more and more in

water supplies, in particular with aggressive water and soil. Nevertheless

much attention has to be paid to an adequate fabrication. Some plastic

materials,

notably poor

polyethylene pipes, serve as nutrient of bacteria.

2-4.5 EXAMPLES OF PRACTICAL, APPLICATION

To show the practical application of chapter 2-4 three different water

samples will be analysed:

Sample

A:

PH = 6,6

Hardness = 2 grains CaC03/gallon

(=2O

DGI

Content of carbon dioxide (CO2) = 20mg/l

This "very soft" water (chapter 2-3.4) is acid (Fig. 11) and "very much

aggressive*’ (Fig. 13 and 14! towards cement and steel products.

Conclusions:

In this water supply project plastic pipes have to be applied and the

concrete

tanks have to be provided with protective coatings. Asbestos

pipes should not be used.

Sample B:

PH

= ,7,4

Hardness = 7 grains CaC03/gallon (=7,7ODG)

Content of carbon dioxide (CO21 = 42 mg/l

This "soft" water (chapter 2-3.4) is little acid (Fig. 11) and "very

aggressive" (Fig. 13 and 14) towards cement and steel products.

Conclusions:

Plastic pipes or coated asbestos pipes (see chapter 2-4.2.3) can be applied.

Steel pipes should only

be

used for parts of the pipeline where other

piping material cannot be applied (e.g. crossing of rocky areas). Concrete

and plastering should

be

protected by additions or coatings. Otherwise the

cement plastering has to be replaced after a few years.

Sample C: PH 1 7,l

Hardness = 11 grains CaCO3/gallon (=10,5O DG)

Content of carbon dioxide (CO2) = 18 mg/l

This “medium hard” water (chapter 2-3.4) is little acid (Fig. 111 and

"little aggressive" (Fig. 13 and 14) towards cement and steel products.

Conclusions:

In this water project all common building.znd piping materials can be

applied.

29

Chapter 3:

INVESTIGATIONS AND BASIC DATA FOR RURAL WATER SUPPLIES

Table of contents

page

3-1

3-2

3-3

3 - 3.1

3 - 3.2

3 - 3.3

3-4

3 - 4.1.

3 - 4.2

3 - 4.3

3 - 4.4

3-5 ANALYSIS

OF

WATER 40

3 - 5.1 Bacteriological. field test 40

3 - 5.2 Chemical analysis of water 41

GENERAL FIELD WORK

SPECIFIC CONSUMPTION

LOCATION OF WATER SOURCE

Source situated above consumer

Spring water

Source situated below consumer

MEASURING OF WATER QUANTITIES

General

Estimating water quantities of a stream

Measuring water quantities with a bucket and a watch

Flow measurements with a weir

3-4.4.1 Thompson weir

3-4.4.2 Rectangular weir

33

34

35

36

37

38

31

3-l GENERAL FIELD WORK

The following list intends to give a summary of the field work during

planning and construction of a rural water supply:

- Application for assistance is sent by the community concerned to the

Community Development Department (CD) or to the local council.

- Meeting will be organized by Community Development Officer (CD01 for

introduction of Department to local officials and community, eventually

forming a project committee.

- Search out water sources (springs, river, etc.)

- Preliminary survey with pocket altimeter, followed by discussion of

the results with the community.

- If the project is feasible collection of more information and data on:

a) Situation: Geographical and administrative situation, place and

function of the village in the region, etc.

b) Population: Number of inhabitants, ethnological composition,

denominations, development of the population during the past years, etc.

c) Infrastructure: Present infrastructure and development plans of roads,

schools, markets, health centres, cooperatives, missions, other

development projects, etc.

d) Economic aspects: Produce and income, cooperatives, agricultural

potential, farms, markets, industries, coordination with other

development projects, etc.

- Contacts to other Government Services, Local Administration

- Measuring of the water quantity of source

- Biological and chemical water tests (see chapter 3-5)

- Detailed survey

- Occurence and quality of local building materials: Sand, gravel,

stones and wood.

- Technical report, estimate (see chapter 5-l)

- Organization of community by Community Development Department (organization

of a project committee if not already done)

- Financing of project:

application for government grants and foreign aid,

commitment to an amount for village contribution

- Organization of community work by project committee and Community

Development Department according to the instructions of the technical staff

- Implementation of project

- Organization of maintenance (see chapter 6)

,

33

,:,,. '

', :

,

3-2 SPECIFIC CONSUMPTION

average daily water consumption

in litres

at present in future

Stage O* Stage I* Stage II*

Village in remote areas per head 25 5r)' 70

Village with school, maternity

and max.lO% private

connections per head 50 70 100

Urban areas with max 20%

private connections per head 50 1c:o 120

Residential areas

(private connections) per head 100 200 250

Primary

school per pupil 10 10 10

College per student 100 120 120

Maternity

per bed 100 100 130

Hospital without Surgery per bed 100 150 150

Hospital with Surgery per bed 200 300 300

The above figures merely give the design engineer a guide to the average

consumptionsi he has to use his own judgement to choose specific consumptions

based on experience in the country and the details of the particular project.

The consumption during one day in rural water supplies can have big variation!

The smaller the community, the greater, in general, is the variation. Market

days and local celebrations can have a big influence on daily water consumptic

The following values have been experienced:

Ratio

Normal

rate Average

Maximum day: average day (from 1.2 to 2.0) : 1 1.5 : 1

Maximum hour: average hour (from 2.0 to 3.0) : 1 2.5 : 1

Measurements in the Ngondzen water supply have shown the same results.

* see chapter 4-1.2.2

Fig. 15 Daily consumption in a rural water supply

Q %

3-3 LOCATION OF WATER SOURCE

3-3.1 SOURCE SX_?~Ui'i'l'ED ABOVE CONSUMER

With all possible water sources have to

be investlqatf~~i

wtrtttlrbr

they can supply wst?r by gravia to the consumer. It is *.ast

prf~fcrdt~lf~ tl,

get water by gravity in order to avoid the installation of an enqinr:

(Imp,

ram, etc. to lift

water to the consumer). In this way the maintcnancr:

will

tJf>

simplified and the running cost kept low; moreover a continuous supply i:;

tJy

far safer.

3-3.2 SPRING WATER

With second priority preference has to be given to spring water

whictl car1 tjf?

caught from inside .the ground avoiding any contamination. In this car:13 no

treatment will be required, which again simplifies the maintcnancc r,f

tllfs

w,ltczr

supply

.

3-3.3 SOURCE SITUATED BELOW CONSUMER

With third priority

sources

have to be investigated which are situated

below the consumer in case of failing to find a source above the village.

But also in this case preference has to be given to spring water

which can

be caught from inside the ground. It has also to be investigated

whether the

water can be lifted to the consumer by natural resources (e.g. water power:

hydraulic ram, possibly turbine, or wind, etc.).

3-4 MEASURING OF WATER QUANTITIES

3-4.1 GENERAL

The most important figure for any kind of water-works is the quantity of

water available.

Before we start detailing a project we need to know how much water has to

be considered.

- for barrage, catchment, overflows

- for intake, sedimentation, filter

Gauging should be done regularly once a week for more than one year if

possible. If only one year measuring is possible, it is a necessity to

measure the water quantity of the

source

as well as the rainfall. Compare

the mtaasured rainfall with available rainfall statistics over a long

period, which helps to determine whether it is a dry or wet year. This

enable@ to decids if the water quantity will be sufficient. In case of a

river, msa@ursment should be taken in the morning as well as in the

afternoon (morning : afternoon w 1 : 0.8).

35

,.

$j& ” ~

,6 ,:

34.2 ESTImTI?$ WATER QUANTITIES Of? A STREAM

:

The quantity

of water flowing steadily In a stream is

Q = quantity of water (m3/sec!)

A = cross-sectional area of flow (m2)

v = velocity of water (m/set)

s = surface: for plastered surfaces = 0,9

for rough rocky surfaces = 0,s

average = 0,6 - 0,8

To estimate the flow of a stream carry out the following procedure:

- determinesthe cross-sectional area of the water flowing in a stream

(average

depth of water x width of stream = A)

- measure

velocity of water:

take the distance that a piece of wood or a leaf travels during one

second (Xm/sec),

out

of three measurements.

- calculate the quantity of water as a result of 1 and 2 Q=Axv

3-4.3 MEASURING WATER QUANTITIES WITH A BUCKET AND A WATCH

This is an easy and exact method for quantities up to 300 (600) l/min.

Procedure:

- One or more pipes, depending on the quantity, are fitted into a temporary

earthdam so that all the water passes through the pipes.

- The flow from one pipe should not exceed a quantity which fills a bucket

in less thar) 3 seconds. .

- Calculate the volume of the bucket if it is not a graduated one.

- Gauge the flow of each pipe three times and enter the results into the

records.

- Calculate the quantity in l/min. or l/set.

36

3-4.4

FLQW MEASUREMENTS WITH A WEIR

3-4.4.1

Thompson weir

This method is suitable for quantities up to about

50

l/see.

The following arrangements have to be made:

Fig. 16

UM. ‘ URR WATfR LEVEL

LW i LOWLR WATER LCVCL

TNf In,& LWL snouw

NEVER BE tllGNfR I’MAN

POINT 2,

- minimum H = 2h

- maximum velocity of water at the gauging rod = 1 m/set

- normally a

900

weir is used x = 2

Y

- important: The gauging rod must be in a distance of at least

3

h from

the weir. The zero point of the rod must be on the same level as the

crest of the weir.

Fig.

17

Discharge over Thomson weir

0 04 0.4 0.6 0 0 1.0 1.2 1.4 I.6 10 2.0 2.2 2.4 2.6 2.0 3.0 3.2 34 3.6 3.0 4.0 44 4.6

0

IN L/SEC

U

IN U5LI;

37

Fig.

18 Discharge oyer Thompson weir

tl- = 11

- 20 cm

t6

14

$ I II

u I2 I

.E I I I I Y I I I

#a 2 &-=90’ h=19om

’

2 4’6

0

10

12 14 16 10 20 22 24 26 20 80

0 in L/SEC.

3-4.4.2 Rectangular weir

'This method is applicable for quantities above 10 l/set.

The following arrangements have to be made:

Fig. 19

PROFILE SalION

xb

r

h

ON

1

2

3

:

!

i

10

11

12

13

14

15

:;

18

1Y

20

22

Pb

28

30

- 1.155

2

I 600

900

0.008 0.014

047 081

Alo 224

266 461

465 805

733 1.270

l.UlO 1.867

1.5% 2.606

2.020

3.50

2.63

4.55

3.34 5.78

4.15 7.18

5.07 8.W

6.10 lo.%

7.25 12.54

0.51 14.75

9.91 17.16

11.43 19.79

13.cq

22.67

14.87

25.76

18.88 32.7

23.47

40.6

20.66

49.6

34.5

59.7

41.0

71.0

- minimum H = 4 h

- maximum velocity of water at the gauging rod = lm/sec

- important: The gauging rod must be in a distance of at least 3 h from

the weir, the zero point of the rod

must

be on the same level as the

cxest of the weir.

- normally the minimum width for a weir should be 50 cm, better 1.00 m

- the crest of the weir must have a sharp edge.

38

Fig. 20 Discharge over rectangular weir

h in '3 i~ll/s

a &r3-L&

$ ::;

$ 6.7 5.1

3 9.4

4 14.4

5 20.1

6 26.5

7 33.3

i 48.6 40.7

10 56.9

ll 65.7

12 74.8

13

14 2::

15 104.6

16

u5.2

ii 137.5 126.2

19

149.2

20 161.0

22 l86

24 2l2

25 225

bin

AAL

26

:

::

:2

38

40

42

44

45

46

48

:;

60

65

70

75

80

85

V

in

l/o

for B -l.oq

239

267

;:

357

z

422

455

490

525

543

561

599

tit

z

1054

2169

la8

1411

%

39

15

t L 1 I I I I

14

I I

EXAMPLE h=lZcm b= BOcm

la-;- FROM TABLE Q = 748 llsec x 08m = 6OOllsec

FROM GFfAPH 0 = 750 llsec x OBm = 600 llsec

I

1 I I

lo 20 30 40 50.60

70

80 90 loo

I / sec. m

‘;-.“: ,I i

3-5 ANALYSIS

OF

WATER

3-5.1 BACTERIQLOGJCAL FIELD TEST (MILLIPO~E,)

Millipore is a membrane microfilter technique for detecting coliform bacteria

and other bacterial organisms in water - the principal criterion of sanitary

quality for public drinking-water. In many cases, the membrane filter method

has made it possible to substitute field testing for laboratory analysis.

A real and reliable information about the quality of water can only be got

if the tests are done over all seasons. This means tests have to be done

in dry season and in rainy season in particular after heavy rains.

Test, procedure with portable water analysis kit and monitors which is availab

with CD-SATA-Helvetas:

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Remove the plastic plugs from a bacteriological monitor and set them

aside.

Carefully insert the syringe valve connection into the bottom ("spoked"

side) of the monitor. Avoid excesz,ive force.

Remove a sterile sampling tube from its sleeve and insert the nylon tip

into the inlet hole of the monitor.

Draw the syringe plunger back slowly on the initial stroke (to avoid the

risk of an "air lock" before the monitor fills with water) and hold the

plunger forward to expel the filtered water from the syringe.

Filter an entire measured amount of sample water through the monitor.

Samples of 100 ml are normal for potable water, but samples of 50 ml are

normal when testing stream-water.

Invert the assembly and draw the last few ml from the filter. Use short,

quick strokes to pull the monitor as dry as possible.

Remove and discard the sampling tube, but do not remove the monitor.

Crack off the ti.p of an ampoule (covered by a short plastic tube), but

do not remove the tip or the tube. Place the forefinger over the end of

In some cases it may be difficult to differentiate between coliform of

fecal origin (from intestines of warm-blooded animals) and coliforms

from other environmental sources. In this case a sample may be incubated

at 44OC for 24 hours. The colonies which are growing under these

Conditions are certainly coliform of fecal origin,

The count should be determined and recorded as the number of coliform

organisms (colonies) per lOOm1 of sample tested. (compare with 2-2.1.2)

For more detailed instructions see "Millipore-Manual".

the plastic tube, as when using a pipette, and break off and discard the

bottom tip of the ampoule.

Remove the monitor from the syringe and insert the bottom tip into the

BOTTOM of the monitor, placing it against the pad beneath the filter.

Release the forefinger and by controlling the pressure of the ampoule

against the pad, allow the medium to flow into the monitor.

Replace the plastic plugs, invert the monitor, and incubate at 35OC I

for 18 to 24 hours. Pry off the monitor top, remove and dry the filter,

and count the coliform colonies which are blue-grey coloured with a

metallic lustre.

3-5.2 CHEMICAL ANALYSIS

OF

WATER

A

general chemical analysis of water has to be carried out by a well equipped

laboratory (e.g. of a hospital or a high school).

For

general analysis a sample of at least 2 litres is required. It should

be

collected in a chemically clean bottle made of good quality (neutral)

glass, practically colourless and fitted with a ground-glass stopper.

In the collection of samples from mineralized sources, the bottle should be

completely filled and the stopper securely fastened.

Samples should be transported to the laboratory with as little delay as

possible and should be kept cool during transport. Chemical analysis should

be started as soon as practicable after the collection of the samples and

in any case should not be delayed

for

more than 72 hours.

Fig. 21 shows the result

of

such a chemical partial analysis of different

CD/SATA-Helvetas water supplies.

If a general chemical analysis is not possible, the design engineer has to

analyse the water by a field test. Additionally the engineer has to find

out from the local population whether the water is potable or not.

Chemical field test (Hach)

With the portable water analysis kit (model CA-24WP) of Hach, which is

available with CD-SATA-Helvetas, the following chemical values can be

measured:

- Content of carbon dioxide (CO2) in mg/l (see 2-3.3)

- Content of dissolved oxygen in mg/l

- Hardness in grain CaCO3/gallon (see 2-3.4)

- PH-value (see 2-3.2)

The test procedure is described in Fig. 22.

41

OIAW~ 35 223

Helvetas Zurich

c-’ - sehweiter Aufbauwerk fiir

EntwickluIlgsl~er

wlalslmob--m

wngNnn*tYOvrnJUOr*w

-ucaewemmNr- FXtnf Doppelproben ksser

betr.

&A.T.A.

Wasserversorguag. Ksmmm

3etrifff: Brief

vom

1,

Derember 1975; Ref. W/ii

m:

Chemische Analyse nach

Angaben

wmw-.

Result

Vemuchsefgebnir - Msultat - Rlsultato

(translation!

Sanplss: five ootties rith 1 litre pure rater, aCditiOt%?+lly

five

Settles with

the very Taxxings each and an admixture 3i calcium ccrznnate.

Chmical malysis and

examinatmn

The

analyzed

samples

are

little acia to neutral and

extremely

soft. They contain

extraordinary

litt+e salts and also very iittle orgnic pollution. All the

samples (but

eeeciafiy "Kai" ana

*‘:ieh”j

heve

3 high anility to dissclve iiira

(lime-aggressive catian dioxide).

&cause of the small hardness (very soft

rater)

ails tha acid character, the

tested waters

are aggressive

?cwards

cement

as well

as

towards

steel.

Dn the

orher hand.

tnare

is

no

q

ejection to the use cf plastic material.

ChemLc8.l water amlysis

Dreignation of tha

estsr aelmas: G==%l - Gsh sehn

PH -U&la

6.6 5.9 6.b

6.0

7.0

Htwdness

(in %G]:

Urbanate hnrdness 0.17 0.17 1.0s 0.1 1.7

Non

carbo~te

hsrdllsss 0 0 0 0 0

Total herdnesr cl.17

0.17

1.45 0.1

I.7

colltent

of (in

as/l):

Sulfate8 60, 1 1 1 1 I

Chlorides Cl 0.5 0.5 0.5 0.5 005

Alkalinity ml/l:

Yethyromnge 0.15 0.2 0.B 0.1

G.75

Lime-eggressive

csrtmn

dioxide

Co,

7.7 37.4

a.6

8.e

11

(Hey-f

tCUdl4

consixrmtifm

in mail 1.6

0.6

0.9

1.6

0.9

Calculated

in

mgjl:

Natrium olWnete

NanCOg

Uagnesium ISg

7 l2 24 5 13

D 0 2.4 0 3.5

Dueoendorf. the gth of December 195

1. Fill the ptsta crteas~rr~ tube H

Iull Wllh the wmw to be IR5ld wd

translw to the mlrirth) boltk bv

p~acmg ttw minhy) bottle over the tube

and turnim the bottle rr$htWietc-up.

2.

Add

one drop of f%dphl)uCin

lndi.

catot solullon.

= 1 mQ!t 001

1. FIII the plawstopene4 00 boltle with

the wmtr to be tesoted by allowing the

water to overflow the battlg far 2 or 3

minutes. Be certrtn there are 1~) air

bubbler present m the bottle.

2. Add the cont@nto al one ~~ttow each

of OisrolveJ OrvQen 1 ReaQe!rrt POW-

dsr and 01palued E)xvQen :

Aeapwrt

Powder. Stopper lirmly and carefully

~0 that no au is trappud rn the bottle.

Sea Nore A. Grip the bottle and sbaka

vigorousiiy to ~IIJR. See Note B. A

flocculmt prmipitate will form. If

u~y~~ IS pmwnt the preclpltate will

be brownish.oranps in color.

3. Allow the sample to stand un111 thr

flue has wttld halfway and leaves thr

half of the bottle clw. Then

shake the bolt16 and ,aQam let it

stand unbl the upper half of the bottlr

)S CIQW. see Nate a

4.

Rumwa the smpper and add the con.

tents of onu pillow of D~swlved Omx-

gen 3 Resgcnt Powder. Carefully

m-stopper and shake to mix. The floe

will dissolve and a yellow color will

develop if orryQen is present. This is

the prepuraf sample.

6. Fill the platic messurrnQ tuba lwsl

full with prt!porrad wmpk and pour it

Olto the mirinQbottlr.

W. Whila swirling the samplr IO mir.

add

PAO Titrant dropwise, countmg arch

drop, until the sample chanyrs from

ysllow IO colorless, The dropper must

be held in a vertical manner, Each

drop is eoual to 1 mrr/l dissolved

orvQml al01. SW Not47 L

tf the result from Step 6 4s very low. such

us 3 mq/l or less. It (s Jdv~wble to test a

IWQW wmple to nbtam a more %anrltwo

rmult. Thcs may be dclne by tltratmp

duectlv m the DO ra~lpls bottle as

f0llwn:

1. tJunQ the preparhlj sample left over

from Stet8 4 abwe. pour off the

cantents ot the 00 bottle untrl the

Ia& just rcaclm tho 3&ml m&k on

ths bottle.

2. Wbllra sw~hy the DO hettle Ia mm

the sample. &d PA0 Tltrant dtopw~re.

countmp mch drop, untd the bwnple

chwges from

yellow lo rolorlasr Edch

drop at PA0 Titrant added 8s quaI to

0 2

rndl dissolved oxygen m thr sam

pte. &e Note

E.

NOTES Dwx~lved Oryga,

A. It 8s a bt trtcky IO stopper the DO

bottle vrlthout tropp:ng an air bubble.

To avotd this problem. tnchne the 00

bottle Jv#tly and

msert

the stu~oet

with a quick thrust. This WIII forts air

bubbles auf. Ilowever. it bubbtes do

become trapped m Steps 2 or 4. the

sample should be dwza,ded and the

lest stuted aver.

9. A small amount of powdered reaQen1

may remam stuck to the bottom of

iha DO bottls et this pomt, but this

will not alfect lhe test.

C. Do not oltow the PA0 Titrant to stand

m direct sunhqht. ~5 it is decompod

Itv ultrar~olsl radtatian.

0. In samples that contain high conce”

tnbons of chloride, such JS seawater,

this floe wrll not settle. However, no

interference is observed as long as the

sample 1s allowed to stand m contact

with the floe for 4 or 5 minutes.

L. A more sensitive twt can be performed

bv using Starch indicator Solution

(Cat. No. 34$.13,

not includnf in kltj

while litratrng the ~lmple wtth PAD

fitrant. 70 uw aflectlvrlv. titrute tha

sample until ths color /us1 bagmr to

thenr from yellow-brown to IiQht

yellow, Add

two

drops of Starch

lndteator Solubon. ContmuP tltretlon,

counting the drops of PA0 Tltrant

unrd the sample colar changes from

blue to colorlms. The total number of

drops of PA0 Tltrant uwd md~cates

IhS exact concentration of dissolved

orvyen in the sampI*.

MODEL CA 24WR

Hdness Test

1. Add 3 drops of Mutter Solution. It&

~WSS 1 and swirl to mlrr

4. Add

llttcmt

Ihqwt,

tt.rrthm

.I a

drop al a time. with %vwl~lmy ul Ihe

mhlrlr) hnttlo WbllS the drrlps JPP

cuunt@d. Urllll the YIIutIcJrl 11, IhC

tnlrmfj bulllr ch;mqw Irr~rrc pwk 10

hlus

Thr Iltrant Ac,lyvnt. tldrdnl-.. 1

druppur sl~uuld t,r IISIII II, ,i Vt A I I

CAL rnanncr and thl? drops shmrlrl br

dlspamed at a rate not tartw than one

drop per smnnd The dropper rhouki

ba held shghtlv above the rap ot thy

mtrmg bottle 50 that It

WIII WYW

come mto corrtxt wt.1 the wle of ttw

nvxmy boftle THIS IS IMPORTANT

5. The hJrdnr%. m gr.r~rls iwr ~JJIIO~I a.

calcium carbonate lCKO3J. 0z equ,?~

to thr number ot drops of i~!rdnt

ft0aQent. Hardness 3 requ~rnl IO brmq

atrrut the color ChJnyr

pH Test

1. Fill ths Iwo glass sample tulres to the

6ml mark with the water sample /r ,s

imperJtrve thaf Ihe t&x! be cornplele~ y

rrnrrd free of dory mlot~onr thdt rwy

hvr been uredprcvrotrdy

2. Add

6 drops of Wide HJnge 1 pH

Intl~cJtor Solutmn to me of the tubes

end zwwl to m,x.

3. Insert the prepared sample an th? rqht

openmg of the color comparator

4. insert the tube of untreated

water

sample m the left openmy of the color

comparator.

6. Hold the color comparator UP to a

I&t such as the sky, a wmda;v. or J

lamp and VIR.‘~ through the two W&R--,

bide m the front. ftolcrts the color (11%

until a color match 1s obta~nril Rrdd

the pH throuyh the scale wmdoiv

NOTE pH

The praEencs a! chlorww an Ihe vrJtrt

mple ~111 cd”w J

slqht

rnlerferenre 1,~

the test. Wemove up IO 50 mQ!I chlr)f~~x?

by addmg one drop of OechlorlnJt~i-q

Solution (Cat. Plo. 1069 13. not ~ncltrrlrd

in kit) to the water sample betorr J&I

lion of rho pH lndrcator

43

4-l

4

- 1,l

4 - 1.2

4 - 1.3

4

- 1.4

4-2

4

-

2.1

4 -

2.2

4

-

2.3

4

-

2.4

4-3

4

-

3.1

4

-

3.2

4

- 3.3

a = 3.4

GENERAL LAY-OUT 49

Syetxm of th? water supply

4-1.1.1 Spring water by gravity

4-1.1.2

Stream water by gravity

4-1.1.3 Spring water bl?low the consumers

4-1.1.4 Supply of ground water

4-1.1.5 Stream below the consumers

4-1.1.6 Rain water storage

49

lMnp0ral lay-out in stagea

4-1,Z.l

Servicxz life

4-1.2.2 tbsign in otago&3

WWIpl@~

Materials and construction methods

50

52

54

WELLS

General

Types of wells

sire of well

Construction methods

4-2.4.1

Native system

4-2.4.2 Dug welis

4-2e4.3

Sunk welle

4-2.4.4

Sinking a tube well

55

56

57

58

SPRING CATCHNHNT

Quality and quantity of spring water

Location of springs

Catchment area

Spring catchment (conetructlon)

4-3.4.2

The 'real' catchment

4-3.4.3

Supply pipe to the inspection chamber

4-3.4.4

inspection chamber

4-3.4.5

Outlet building

4-3.4.6 Common mistakes on spring catchment

WATER POTNT

cawrwl

Construction of a water point

65

66

67

70

78

45

4 - 5.2

4 - 5.3

4-6

4 - 6.1

4 - 6.2

4 - 6.3

4 - 6.4

4 - 6.5 Treatment station: Lay-out

97

4-7

4 - 7.1

4 - 7.2

4 - 7.3

4-8

4 - 8.1

4 - 8.2

4 - 8.3

BARRAGE

AND RIVER INTAKE

Determining magnitudes for the position of the

barrage

Design of barrages

Design of intakes

80

81

02

WATER

TREATMENT

General

Sedimentation

4-6.2.1 Definition general

4-6.2.2 Design of sedimentation tanks

4-6.2.3 Construction details

03

83

03

Slow sand filter

4-6.3.1 Mode of action

4-6.3.2 Hydraulic system

4-6.3.3

Size and number of filters

4-6.3.4 Construction details

Other filter types

4-6.4.1 Rapid gravity filter

4-6.4.2 Pressure filter

STORAGE

General

Capacity of a storage tank

Design of storage tanks

DISTRIBUI'ION SYSTEM

Lay-out of the distribution system

4-8.1.1 Type of distribution systems

4-8.1.2 Pressure zones

4-8.1.3 Disposition of taps

Piping material

4-8.2.1 General

4-8.2.2 Asbestos cement pipes

4-8.2.3 Plastic pipes

4-8.2.4

Steelpipes

4-8.2.5 Valves

Design

of the distribution system

4-8.3.3 Hydraulic calculation of piping

4-8.3.2 Prevention of air pockets

g-8.3.3 Prevention of vacuum

4-8.3.4

Air

release valves and anti vacuum valves

90

96

99

101

103

105

110

46

4 - 8.4

4 - 8.5

4-9

4 - 9.1

4 - 9.2

4 - 9.3

4 - 9.4

Implementation

4-8.4.1 Trenching

4-0.4.2 Laying of pipes

4-8.4.3 Thrust blocks and anchoring

4-8.4.4 Pressure test of the pipeline

4-8.4.5 Valve chambers

4-8.4.6 Pipe connections to buildings

Distribution buildings

4-8.5.1 Public standpipe

4-8.5.2 Public washplaces

4-8.5.3 Public shower house

1.20

135

WATER LIFTING 139

Types of pumps

Hand pumps

4-9.2.1 Deep well pump

4-9.2.2 Wing pump

139

140

Centrifugal pumps 143

4-9.3.1 Planning of centrifugal pump installations

4-9.3.2 Pump drives

4-9.3.3 Pumping stations

4-9.3.4 Data needed by an enquirer

Other pumping system

4-9.4.1 Hydraulic ram

4-9.4.2 Hydro pump

148

4-l GENERAL LAY-OUT

The results of the investigations in the field (chapter 3-l) have to be

compiled and different solutions have to be compared with respect to

economy, technique, maintenance, running cost etc. It depends on the

skill of the engineer to find an optimal lay-out. In the following a brief

guideline and a few examples will be given.

4-1.1 SYSTEM OF THE WATER SUPPLY

The available water has to be compared with the actual water consumption

as well as with the expected water consumption in future. The balances

of water have to be determined in the water budget. In accordance to the

balance oE water the water source to supply the village is chosen. The

system of the water scheme is decided accordingly with regard to the

simpiest, clearest and most appropriate lay-out. Special attention has

to be given to a simple maintenance as described below.

4-1.1.1 Spring water by gravity

In this case the 'spring water' will be caught inside the ground (see

chapter 4-3.4). Preference is always given to this system because it is

the simplest : It supplies water of best quality, requires little

maintenance, keeps running cost low and gives greatest safety. That's

why it is applied no matter whether the spring is situated in a far

distance or not and accordingly the cost of construction may even be higher

than the cost of a water supply from a nearby stream (incl. treatment

station).

In case the available spring water is sufficient only to supply part of

the required quantity of water for stage 1 of the project, water will

still be supplied from this spring in a first phase. During the dry

season the

water

consumption may be restricted to drinking and cooking

purposes only and washing may still have to be done in a nearby stream.

4-1.1.2 Stream water by gravity

Preference will be given to an open stream which can supply water by

gravity in case there is no spring available higher than the village.

Its advantages are almost the same as 4-1.1.1 . But a treatment station

cansisting of sedimentation basins and slow sand filters is usually

required.

4-1.1.3 Spring situated below the consumers

5 I

In case there is

no

way to supply water by gravity (e.g. if the village

is situated on the top of a hill) preference will be given to a spring

which can supply water of good quality.

a)

Water

is collected from the source by the consumer

In or'der to ensure good quality of water and some storage facility

a

water

point (see chapter 4-4) is constructed.

b)

(see chapter 4-9)

There

are different possibilities to do this. Preference will be given

to natural driving energy (e.g. water power: hydraulic ram, water

turbine or wind etc.).

4-1.1.4 mly

of

ground

water

Underground water is usually of good quality if the covering stratum is

waterproof. The catchment consists of a well construction (see chapter

4-2). Except of an artesian well the ground water has to

be

lifted before

it can be consumed. In remote areas the ground water is usually lifted

either by a bucket on a chain or by a handpump,

but

only to the surface

from where it is carried to the houses.

4-1.1.5 Stream situated below the consumers

In case of failing to get water supplied from a source as described

above, this system may be applied.

But

this system requires skilled

maintenance and the running cost will be high. That's why this system

should only be applied in areas where the maintenance is assured

technically and financially.

4-l .I. 6

Pain

water storage

In

areas where no springs , streams and no ground water are existing

rain water may be stored to supply drinking-water. The storage capacity

has to be calculated according to a maximum length of the dry season. Tile

minimal water consumption for drinking and cooking use only (no washing,

bathing etc.) should be calculated with 10 - 15 liters per person and

day.

In tropical climate the rain water whould be stored in covered cisterns

(without any light) and it should be kept as cool as possible. The rain

water stored for a long period needs to be treated before consumption

(preferably by small slow sand filters). Such a system consists

usually

ot the waterproof catchment area, the seasonal storage tank, the small

treatment station and a little storage tank for the daily consumption.

4-1.2 TEMPORAL LAY-OUT IN STAGES

After the system of the water supply

has

been decided upon, the engineer

has to consider which stage the various elements of the system have to

be designed for. He has to consider the actual project cost, the running

cost, the expected increase of the population, their financial situation,

the facility of extension and the durability ('service life') of the

various elements.

50

4-1.2.1 Service-_life

Etvery element of a water supply can be used in good working order during

a certain duration

of

time only. This period is called the 'service life'

of this element.

The following list shows the service life of different elements of a rural

water supply. These declarations are experience-data of solidly constructed

elements under skilled maintenance:

Element

spring- and stream catchment

storage tank, treatment station

buildings (in concrete or masonry)

installations

under ground pipes

pumps, engines

expected

service

1 ife

30 - 50 years

over 50 years

10 - 20 years

over 50 years

10 - 20 years

4-1.2.2 Design in stages

At

first the different stages are defined:

Stage 0: Actual stage -, present population as base of the

calculations for the future development.

Stage I: This is the moment when the village has the

double

population (2 x the actual population).

This is equal to a yearly increase in population of 3%,

within 24 years. Also the future development of industries,

markets, cattle-ranges, roads, colleges, hospitals, etc.

has to be taken into consideration.

A

co-n village in

the rural area

of

the U.R.C. will reach stage I within

20 - 25 years. In a

very

fast growing village, a regional

centre with functions of a rural centre, stage I may be

reached within 15 years.

Stage II:

A

water supply designed for stage II is able to provide

water to a population four times the actual population.

This moment will be reached within 30 - 50 years.

Compare with 'specific consumption', chapter 3-2.

The different elements of a water supply for a village in the rural

area

are

usually designed

for

the following stages:

Element

Catchment

intake

inetallatione

PLping eystein

main pLpee

d&rtribution pipee

Starage tank, treatment station

buildings

inetallatlons

pmpsr engines

0 Stage

X

x

X

I Stage Stage II

X

X x

X

x X

x

x with extension facility

X

El

4-1.3 EXAMPLES

Before the single elements can be designed, a clear lay-out of the whole

water supply has to be worked out. This base for the calculations should

be included in the technical report.

Example ,&

Short description of the water supply:

A rich spring situated above the village.

Actual population 2'000 persons.

Expected water consumption:

Stage 0: 2'000 persons at 30 l/day = 60 m3/day to,7 l/s)

Stage I: 4'000 persons at 60 l/day = 240 m3/day (2,8 l/s)

Stage II: 8'000 persons at 80 l/day = 640 m3/day (7,4 l/s)

Water balance:

The yield of the spring is over 800 m3/day at the end of the

dry season. This is enough to cover the whole consumption of

the stage II.

Lay-out of the water supply

I

Example 2

1 Spring catchment with inspection chamber

designed for stage II.

2 Pipe line calculated for stage II

(q=7,4 l/s).

3 Interruption chamber. After stage I

a storage tank has to be constructed

at this site.

4 Main pipe. Calculated for stage I

without storage tanks and for stage II

with two storage tanks (q=lO l/s).

5 For stage II an additional storage tank

is required.

6 Distribution pipe, calculated for stage I.

7 Any likely extension would have to be

included into the calculations.

Short description of the water supply:

A spring situated above the village.

Actual population 800 persons.

Expected water consumption:

Stage 0: 800 persons at 25 l/day = 20 m3/day (O,2 l/s)

Stage I: 1'600 persons at 50 l/day = 80 m3/day (0,9 l/s)

Stage II: 3'200 persons at 70 l/day = 224 m3/day (2,6 l/s)

52

Water balance:

The yield of the spring is 50 m3/day at the end of the dry season

and about 140 m3/day at the peak of the rainy season. During the

dry season in stage I the consumption has to be limited. For stage II

the yield of this spring is not sufficient.

Lay-out of the water supply:

1 Spring catchment with inspection chamber

designed for stage I.

2 Transport pipe designed for stage I

(q=O,9 l/s).

3 Storage tank calculated for stage I

(capacity about 40 m3).

4 Supply pipe, calculated for the peak-

consumption of stage I (q = 3 l/s).

Example 3

Short description of the water supply:

No spring available, the stream is below the village.

Actual population 1'400 persons.

Expected water consumption:

Stage 0: 1'400 persons at 25 l/day = 35 m3/day

to,4

l/s)

Stage I: 2'800 persons at 40 l/day* = 112 m3/day (1,3 l/s)

Stage II: 5'600 persons at 50 l/day* = 280 m3/day

(3,2 l/s)

(* = reduced due to high running cost)

Water balance:

The stream yields during the dry season at least 15 l/s. Therefore

the consumption of stage II can be covered.

Lay-out of the water supply

. .

1 Stream catchment with a short-time-

sedimentation.

dam and intake for stage II

TER

sedimentation for stage I

After stage I this is the proposed site

for a pumping station.

2 Driving pipe and hydro ram calculated

for stage I. The driving water is not

sufficient for stage II. Therefore

after stage I the hydro ram has to be

replaced by a pumping station at site 1.

3 Pressure pipe, calculated for stage I

(q = 1,3 l/s).

53

4 Treatment station: Sedimentation and slow sand filters designed

for stage I (q = 1,3 l/s) with extension facilities.

Storage tank for stage I (capacity about 60 m3).

5 After stage I an additional storage tank is required.

6 Main supply pipe, calculated for stage II.

7 Distribution pipe, calculated for stage I.

4-1.4 MATERIALS AND CONSTRUCTION METHODS

The materials and construction methods have to be chosen according to

local availability and to the skill of local workmen (e.g. stony area

but no gravel-c stone masonry, unamployment *labour intensive method etc) .

The skill of local workmen has to be developped in such a way that all

constructions are done in best quality in order to increase their lifetime.

Much attention has to be paid to the possible aggressivity of water in

choosing the piping material as well as in designing the watertight coat in

tanks etc. (see chapter 2-3 and 2-4)

54

4-2 WELLS

4-2.1 GENERAL

Wells make it possible to use the underground water for economical

applications (e.g. water supplies, irrigation).

The quality of the water obtained from a well depends on:

- The thickness of the stratum which covers the water-bearing soil.

This is important because of indirect contaminations for example

by latrines, fertilizers etc.

- The porosity of the subsoil which influences the natural filtration

process.

Fig. 23

Point a I suriaa

vatmahod

Point b I subtrrrumaa ntwahad

The quantity of water obtainable from a well depends on:

- The intake area: It is important to realize that the topographical basin

does not necessarily correspond with the geological or hydrological

drainage area. (see Fig. 23)

- The annual rainfall percolation: this depends on the nature of the intake

area, e.g. kind of vegetation (forest, farm, bush)

- The perviousness of the ground: this depends on the kind of material

stratification and its homogeneity.

- The storage capability of the ground: this depends on the same factors

as perviousness and intake area.

- Type of well: its diameter and depth.

55

4-2.2 TYPES OF WELLS

Fig. 24

-

m Pelw4bla

otrrt4

a-

4b4llowwell

lzzil

fipprrumablr rtmta

b -

deep

wall

01 artaaiianwrll

a) Shallow well

The shallow well draws its water from the permeable strata between surface

and soil. The storage possibility in this upper permeable strata is very

limited and consequently the capacity of such a well is unreliable and

probably intermittent. The well is supplied by surface water which is

liable to pollution (no natural filtration). A shallow well should be

lined with impervious material to within a few meters of the bottom.

b) Deep well

The supply is-derived from strata unaffected by surface impurities. There is

at least one impervious stratum between the water-bearing stratum and the

surface water (natural filtration). It is however possible for surface water

from the upper strata to gain access to the well through cracks and joints

in the impervious stratum. Compared to a shallow well the yield of a deep

well will be much more dependable. The yield will be greatest when the well

has just been opened. If the water has to pass through a porous stratum

before it reaches the well the pores tend to become choked in time and the

flow is considerably reduced. This does not occur with limestone or volcanic

stone as the water finds its way through cracks and fissures and gradually

dissolves the rocks so that the voids are increas,d.

cl Artesian well

These have similar characteristics to deep wel.ls, the essential difference

being that the underground water is tapped under pressure and may rise to

the surface of the ground under its own head.

well is rarely found in Cameroon.

56

I’

,p;

i l’

4-2.3 SITE OF' WELL

1 It is not always easy to determine the site of a well. Only test

boreholes could give certain information, but in general in large plane

/

areas or near the sea shore, the river or lake,we can be sure to reach

a water table within a certain limit.

Choosing d good well site is one of the most important phases in well

construction. The site should be also placed in a well drained ground,

avoiding the vicinity of overhanging trees.

Fig. 25 Siting to prevent poilution

a a = bad site for shallow well = bad site for shallow well

b = suitable site for shallow well b = suitable site for shallow well

C C

= latrine = latrine

d d = flow direction = flow direction

The site of a well should be upstream of any possible

of pollution. of pollution. source

CONSTRUCTION WETHODS

4-2.4.1 Traditional

This well consist of a hole with a diameter of 00 to 120 cm. The life

of such wells is short because there is no protection of the walls and

the surface around the wells.

4-2.4.2 Dug wells

These wells are protected during construction by consolidating the surface.

After a certain depth is reached the walls will be secured either by

cpnccete or masonry before digging deeper.

A

dug well is usually constructed with a diameter from 90 to 300cm. It

can be dug to depths of about 60 to 80 m.

The site should be carefully chosen. It should be at a good distance from

any

possible

source

of contamination. Areas known to contain rock layers

should be avoided

if

possible.

It has been found that the cost of a lined well varies in proportion to

its diameter. The minimum diameter is limited by the room available for

one or several men to work in. A diameter of

about 90

to 100 cm

is

necessary for one man and 120 to 130 cm for tw men. It has also been

found that the efficiency of two diggers working togethor is more than

twice that of a single man, we can then

say

that a diameter of 120 to

13Ocm is a convenient standard size.

With the exception af wells sunk into consolidated rock, a lining of

permanent material is always necessary. This lining serves several purposesr

it is a protection against caving in

and

collapses, it retains the walls

after completion. It is better to build a permanent lining already during

construction thus avoiding the expense

of

temporary supports and the danger

of collapse which may occur when the temporary lining is removed. Reinforced

concrete is usually employed for the lining.

In normal ground the shaft is sunk from ground level to the top of the

water level by the method known as "alternate sinking and lining". The hole

is excavated and trimmed to a diameter of 120 to 130cm and depth depending

upon

soil conditions. The excavation can be done as deep as it is possible

without endangering the workers in the well. In

any

case the first meter dug

should be secured properly before the digging continuesi This met$od is

applied until the water level is reached. From this depth onward! -.he caisson

--

ring method is adopted, The caissons have to be precast on the sl*rEcrce. Thr?

caissons should have a height of no more than 50cm. These caisson-rings

are

lowered singly into the lined well and each one is fastened to the ring below

The depth to which the caisson-rings can be lowered depends on the depth of

water which can be removed by bailing. (see Fig. 26)

58

Fig.

26 hrkinq method

for

a dug- w&J

2 3

water-pi

-- -L-L-

5 6

b)

Precautions during the construction

1. Digging as deep as

possible, according to

the soil conditions

2. Concrete lining

3. Digging as deep as

possible or until

the water-level is

reached

4. Concrete lining

5. Lowering of caisson ring,

digging continuously

6. Lowering of caisson rings

digging as deep as

possible into the water.

This job has to be carriet

out during the driest

period of the year when

the water table is at its

lowest point.

The following points are very important. They should help to prevent

accidents.

Most of the accidents in a well are caused

by:

collapse of walls which are not

lined properly

Nobody should work alone in a

well. In case of an accident

the workman on top should

organize aid. If possible the

workman

who works inaide the

well rhauld be secured with a

Falling into the well.

Sudden collapse of water1

danger of drowning

Before entering the well, make sure

that there is no accumulation of

sulfuric or carbonic gas.

Introduce a lit lamp (kerosene) into

the well. If the flame dies it means

that there is gas and danger.

This gas can be removed either by

sending air down into the well with a

compressor or by using a bunch of

grass or paper tied to a rope as a

fan by twisting it energetically.

Never place a combustion engine

inside or near a well as the carbonic

exhaust gas being heavier than air will

fill the well and endanger the workers.

It is always advisable to construct

a protection at ground level all around

the well in order to prevent accidents.

60

--I - Porous STRATUM

The superstructure or sealing of a well

must bc done wry

carefully.

It

is ilt@Xtant to look for a good drainage for

excess water; furtht?rrn(Jr':,

the well should

always

be completely sealed except for a man

hole. If

possible a hand pump should be installed to avoid conta~~~inatiorl ~.jt

tttv

water

with buckets

(see chapter 4-9).

Fig. 27

HAND -

PUMP

WASTE WATER

In case water should be lifted

with bucket an pulley, a

margelle must

be

built at

70 - 90

cm above ground level.

A cement apron around it will

keep the place free of

stagnant water.

MARGELLE

AQUIFERE

4 AT LEAST

DEEP

ZONE

2m

61

4-2,4,3

link wells

These wells consist of prefabricated rings which sink through their own

weight ,a8 soon as digging is done. This system cannot be applied in all

types of ground.

But

it is very good

for

homogeneous ground (e.g. sand). '

CONCREtE RING

(WATERTIGHT)

WATER TABLE

CONCRETE RING :-

(POROUS) r

SINK WELL

,

WORKING ORDER

1

V

IRON CUTTlhG EDGE

4-2.4.4 Sinking a tube well

In

areas

where the subsoil is sandy and the water table situated between

5 to 20 m deep, there is a good possibility to sink a well without using

a drilling machine nor any other machine. All that is needed are a few

bamboo or other wooden poles, several lengths of rope, sufficient water

to fill the pipe, an iron beak (with a small hole on the side), a plastic

filter of 1,20 to 2,00 m and the necessary tools and fittings for joining

the pipes together.

A team

of three men is sufficient for sinking a tube well of a size up to

5 cm diameter and 15 m depth. Bigger diameter and greater depth require

more

people.

62

Procedure of sinking:

Once the site

of the well is chosen, dig the soil about 30 cm deep in a

diameter of 2,00 meters; moisten the hole with water, install a small

scafolding and tie a pipeetjuippedwith an iron beak at the bottom

(see Fig. 28a). Move the lever in order to have a perpendicular up and

down movement. The pipe will sink with these movements provided it is

filled with water.

The sinking continues; the next pipe element is screwed to the first one

and so on, until it reaches the water table (see Fig. 28b and 28~).

If pressure water is available and can be fixed directly to the top of

the pipe, the sinking can be done much faster. The structure of the

subsoil is the main factor for sinking a well. If rock or other hard soil

is found a new site for the well has to be chosen.

As soon as the pipe has reached the water table it is necessary to remove

it entirely by lifting it carefully (see Fig. 28d). (note that the hole

created is about 15 to 25 cm diameter) . This operation is needed to allow

the filter to be placed at the head of the pipe instead of the iron &dk.

The tube well is sunk. Fine gravel or coarse sand should be placed into

the space between the tube and the soil. A hang pump or motor pump can

now be installed. A shallow pump (with the plunger situated above the

ground)

will

be

able

to lift water from a depth of 6,50 meter maximum.

For depth greater than 6,50 m a deep well pump has to be chosen and the

diameter of the suction pipe must be big enough to allow the plunger

cylinder to enter it.

Fig.

28a

Fig. 28b

63

28 c Fig. 28

d Fig. 28 e

-- --- -

- -- c-

__--- - -

- --

--

- --

1

x low& w&r table --

-- - -

.

-m-w---

64

.

4-3

SPRING CATCHMENT

General description of springs: See chapter 2-1.2 'Springs'.

4-3.1 QUALITY AND QUANTITY OF SPRING WATER

The quality of spring-water depends on factors similar to those in a

continuously flowing spring:

- The thickness of the stratum which covers the water-bearing soil: this

is important to prevent indirect contamination (e.g. from latrines,

fertilizer).

- The perviousness influences the natural filtration process.

- The storage capability influences the water velocity. If the water

velocity in the saturated stratum gets too high, the pores through

which the water passes tend to become choked so that the flow becomes

considerably reduced, This does not occur in limestone or in volcanic

rock.

As continuous flow and quality of a spring depend on the same factors, we

take the relation between

spring capacity in the rainy season

spring capacity in the dry season

=

3- 5 for good springs

as a criterion for the quality and quantity which is available.

There is a time interval between maximum/minimum rainfall and maximum/minimum

yield of a spring. This means that the lowest yield should not be expected at

the end of the

dry

season but 2 to 4 months later.

The springs intended to feed a water supply should be gauged before constructio

starts for at least one year but better over a longer period.

The water temperature may also give some information about the quality of the

spring: E.g. in the grass land zone of Cameroon an underground source of good

quality shows a temperature of 18oC (if it is not in a volcanic area).

Especially the way the water-temperature changes during a day informs about

the quality of the spring. Spring water of good quality will show constant

temperature.

A

special problem in the grassland:

Raffia bushes cause the growing of ferric bacteria in supplying carbon

hydrates. In connection with air the ferric bacteria develop rapidly and

cause a coloration (red) and an unpleasant taste although the water is still

harmless to human beings. In order to avoid this occurance, springs should

always be caught above raffia bushes.

65

4-3.2 LOCATION OF SPRINGS

We distinguish three zones:

Grass-land - Forest - Volcanic

areas

In grass-lands, springs are mainly found in valleys and along streams

inside raffia bushes.

In forest areas, springs usually appear at the bottom of valleys, but it

is difficult to locate them because rich vegetation covers everything.

In volcanic areas, springs can suddenly appear and disappear almost

anywhere, especially during and after eruption or earthquakes.

Geological springs normally appear

- Where the impermeable stratum reaches the surface

- Where two different kinds of subsoil meet

- Where topsoil meets rock

Tracing of springs:

Villagers and hunters, who know the area, may be most able to give

information about the possible water sources.

In addition it is often necessary to follow all streams and springs to

discover the rising points, where the possibility of construction of a

spring catchment has to be investigated. Sometimes it may be essential

to measure the change of the water quantity along the stream in order

to discover possible underground side drains.

Most important is to investigate on the area above the rising point of

the spring, because it may happen that an open stream sinks into the

ground above the rising point and passes underground before reappearing

on the surface as a spring. That is why it is also necessary to gauge

the yield of the spring over the whole year. Special attention should

be given to the yield of the spring and the colour ot the water after

heavy rains. If abrupt increase of flow or change of colour or temperature

of the water is discovered, it is, proved that short connection to the

surface does exist and that accordingly the spring is certainly not of

reliable quality.

66

4-3.3 CATCHMENT AREA

The catchment area includes the area which is situated above the

catchment and may drain into it. This area has to be established as

protective zone. The radius of the protective zone from the catchment

depends on the depth of the spring catchment and the nature of the

covering stratum. The radius should be the bigger the shallower the

spring catchment is and the more permeable the covering stratum is, but

at least 50 m.

Within this area strictly no farming, no domestic animal grazing, no fish

ponds, no rubbish pits (oil), no stables or houses, etc. are allowed.

Existing streams and drains situated in the catchment area have to be

made water-tight. In case of danger that surface water may enter the

spring catchment or may cause erosion, it has to be drained off.

To have a good control

over

the protective area it is advisable to plant

grass within a radius of 10 m and keep it cut short. Outside of this

radius the protective area should be afforested. Attention has to be

given to the fact that some trees like Eucalyptus suck much water and

are, therefore, not useful in this zone. Suitable trees are for instance

Cypress or Pine trees. It is also advisable to fence the area with barbed

wire. In areas with long dry seasons attention has to be given to protect

the afforested area from bushfires.

In an extended protective area (water intake area above the spring:

Radius 100 to 200m) there should be no petrol-stations or workshops where

waste mineral oil or petrol are thrown away. Also no fertilizer should be

used within this area. It is advisable to afforest the extended protective

area too.

4-3.4 SPRING CATCHMHNT

4-3.4.1 General

A spring catchment has to be constructed in a simple and practical way. It

depends on the topographical situation, the structure of the ground and

the type of source.

No attempt should be made to change the spring's natural flow rate. If there

is any obstruction the spring can get dirty or the water will try to find

another route.

The installation has to be carefully built to avoid the possibility of

water pollution by accident or negligence or even on purpose.

The depth and the construction of the catchment depend on geological and

hygienic consideration as well as on material covering the water-bearing

soil. The spring catchment should be covered at least by 3 m. If it is not

possible to cover it properly, it is necessary to make special protective

arrangements. If possible the catchment should be built right up to the

impermeable strata. Blasting near springs should be avoided. The free flow

of the water must be guaranteed during the construction.

67

There are three main parts in a spring catchment:

- The actual catchment (perforated pipes

or

a channel built with dry walls)

- The supply pipe to the inspection chamber

- The inspection chamber (not to be confused with the storage tank)

The inspection chamber has two parts:

an entrance basin for the water and

an operation chamber for the appropriate installation

The purpose of the inspection chamber is to control water quantity and

quality (sometimes by sedimentation).

Fig. 29 Spring catchnent - Lau-out

ORAIM FOR SUlFhCE WATER

MAllUS FOR CATCNMENT OIRECTION

MAIN FOR .uJRFRCE

WATER

- 8OUNDARY MARUS FOR PROTECTIVE ZONE

ORAIM PIPE (IF NECE SSAIIY)

SUPPLY PlPE

kk -

rr

1

.-I

r

--

68

4-3.4.2 The actual catchment

It is important to construct the catchment most carefully because it is

the heart of the water supply. In case of failure to do so, it may cause a

total breakdown of the entire water supply. Moreover the catchment will not

be accessible after backfilling.

Much experience is required to interpret the flow of the source underground

and to design and construct the catchment accordingly.

a) Excavation

Normally the digging on the source is started on the point where the water

comes out of the ground. While following the flow of the source into the

ground a drain has always to be kept open to ensure a free flow off. This

is required to avoid any increase of pressure of the source inside the

ground and hereby forcing it to find another way out which may not be

controlled anymore. Moreover, this provision will enable the technician to

have a clear picture of the direction of the flow of the source.

The few following examples are given as a guideline:

Example 1:

The amount of water coming out at the mouth of the trench decreases with

digging. Therefore, water is entering on one or both sides along the trench.

In this case the trench has to be split up in a V or T shape to the two

sides as soon as the cover on the mouth of the trench is big enough. In this

way the bypassing water may be caught behind the dam with sufficient cover.

Example 2:

Spring water is coming up from

the ground. The drain has to be

dug down till the horizontal layer

is discovered out of which the

water is originating. In case the

cover is insufficient the excavation

has to follow the source level till

the cover becomes sufficient (at

least 3m).

3m

Example 3:

In case the drain cannot be dug as

deep as the horizontal layer the

construction has to be done like

for an artesian well.

Example 4:

Much care has to be taken during

excavation not to cut through the

impermeable layer on which the

source is running. Otherwise the

source water may penetrate into

the permeable stratum below.

Therefore the foundation of the

dam has to be cast into the

excavation directly against the

ground, before the dam is built

in masonry or concrete.

Example 5:

’ . ‘, .

I . . . ;

The distance between the catchment and any tl ? should be

large

enough

to be sure that no roots can enter the catchment.

b) Building

Once the excavation is completed the building work can be started. There are

two parts: A permeable construction into which the water enters and a

barrage which has to avoid the bypassing of water.

- The permeable construction consists usually of a drain in dry stone masonry

or perforated pipes. The cross section of this catchment drain should be

sufficiently large to ensure the maximum out-flow without any obstruction

to the natural spring flow. The drain has to be sloped 1 to 2%. In case of

firm ground no flooring is done. But in case of sandy ground a dry pavement

has to be foreseen. The speed of water should be limited by providing

additional catchment drains, because the speed increases the drag force of

the water.

Around the drains a filter will be built with gravel. The minimum diameter

of

the

gravel has to be in relation to the holes of the perforated pipes

or the spaces in the dry wall. To avoid any contamination never walk on

this

gravel.

A water tight cover of 5 to 1Ocm concrete has to be placed on the top of

the drains and the gravel. This cover needs to be extended on all sides

20cm into the walls. Syrface water reaching this cover needs to be drained

off.

-

The

barrage

is constructed

on

the opposite side of the point where the water

is entering into the catchment. It guides the water to enter the supply pipe

"leading to the inspection chamber. The barrage has to

be

built into the

impermeable stratum as well as into both side walls to prevent the water fro1

A“,

I' byjas'sing. The foundation of the barrage (dam) is cast into the excavation

directly against the ground in order to get a tight connection to the ground

The barrage is constructed on top of the foundation, either in concrete or

stone masonry.

The height of the

darn

should only be to the height of the

water-tight cover which is on top of the drainage.

Compare with figures 30 and 31

Fig. 30 Spring catchment in line

4 5 6

IMPERMEABLE STRATA 6 GRAVEL

WATER- BEARING SOIL 9 WATER-TIGHT COVER

COVER OF WATER BEARING SOIL 10 DAM

BED PLATE l-2 x 11 PERMEABLE MATERIAL

DRY WALL 12 IMPERMEABLE BACKFILLING

SLABS 13 SUPPLY PIPE 2 x

PERFORATED PIPE 14 DRAIN FOR SURFACE WATER

PLAN

CROSS- SECTION TYPE 1 CROSS - SECTION TYPE 2

1

9

6

,

,’

Fig. 31 Spriklg

ca

tchtnent in shape of a T

SECTIONAL

ELEVATION - __ -I_-- ---

--- - -I_- - - --

----v- - -

- -

’

-

- -.-

5 6 9 11 12

1 IMPERMEABLE STRATA 8 GRAVEL

2 WATER- BEARING SOIL 9 WATERTIGHT COVER

3 COVER OF WATER-BEARING SOIL 10 DAM

4 BED PLATE (l-2 X

J

11 PERMEABLE MATERIAL

5 DRY WALL 12 IMPERMEABLE

6 SLABS BACKFILLING

13 SUPPLY PlPEs(2 L)

7 PERFORATED PIPES 14 DRAIN FOR SURFACE WATER

CROSS-SECTION CROSS -SECTION

COLLECTION CHAMBER

72

5 8 10

14

4-3.4.3

Supply pipe to the inspection chamber

The piping material has to be resistant to aggressive water. The pipe

should slope at least 2%. The diameter of the pipe has to

be

according

to the maximum yield of the source, but at least 8Onun. It is advisable

to install one additional pipe in reserve. This extra pipe should be

installed a bit higher than the first one, so that the carctaker

knows

when the first pipe is not working that a failure has occured which he

has to follow up. The installation of an extra pipe is necessary

because

once the catchment is blocked,' the source will build up pressure behind

the catchmcnt and force another outlet. This may cause an unrepairable

failure because the source may disappear completely.

4-3.4.4 Inspection chamber

Every catchment should be equipped with an inspection chamber to allow

easy access to the spring. The chamber should not be too small to ensurs

sufficient

room

for all the installation works.

It may be necessary to calculate the inspection chamber as a small

sedimentation chamber with a retention time of 10 minutes.

The building has to be water-tight inside and outside. Corners and edges

have to be rounded. Each chamber should be ventilated, if Possible in

combination with a drain-pipe

or

an entrance. Ventilators and manholes

should not be directly above the water , they should rather be placed in

the operation room. Entrances or manholes should be 50 cm above ground-

level with door-steps at 25 cm. Manhole covers should be locked to

prevent unauthorized Persons from opening them. It is advisable to cover

the chamber (incl. entrance) and all openings (incl. overflow and doors)

so as to prevent any Possibility of Pollution and the entering of small

animals into the chamber.

Each spring cat&sent needs its own entrance basin, from where the water

flows into a collection basin. If necessary it should be Possible to cut

off a single spring from the supply.

The inlet must be 20 cm above the highest Possible water level.It is imPortaM

that each basin can be drained.Thereshould be no obstruction to the water

flow caused by placing the inspection chamber too high in relation to the

spring.

The dimensions of overflows and drains have to be capable of draining off

the maximum spring capacity without restricting spring flow.

Note:

For

hygienic reasons, it is important that timber is not used as a

building material and that no timber is left in the catchment or inspection

chamber (the timber gets rotten and will become a breeding place for

insects).

Stone masonry and concrete seem to be the most suitable and long-lasting

building materials for spring catchments. Buildings in stone masonry may

require an outside plastering ,:u,?t in a swampy area. The chemical behaviour

of the water and the ground influences the building material (see chapters

2-3

and 2-4).

See figures 32 and 33

73

Inspection ch+mber

6

=+==-

‘f WATERPRODF PLASKRING

INTERNAL AND EXTERNAL

_'

I'

I',,

1 Pipe from the spring catchment

2 Baffle plate

3 Overflow pipe

4 Overflow edge

5 Cleaning pipe

6 Supply pipe to consumer

7

Drain

pipe

8 Ventilation (with wire net)

9 Aeration pipe

10 Climbing iron

11 Strainer

12 Main

valve

13 Entrance (Min 60 x 70 cm)

74

Fig. 33 Inspection and collection chamber

(Incl. connection of

an

upper catchment which has dlready ~II inspection

chamber. An additional overflow may be foreseen in the entrance in case

of much overflow expected from lower source in order to get sufficient

retention time in the entrance basin.)

/.

,’

I,I

I

/

. ‘.

-

.’

/’ ,’

,I’

/’

t

,/’

2

,/--- ENTRANCE

( min.Wx70cm)

FROM LOWER /’

2

L

1

8

- VENTILATION

(WITH WIRE NET )

SUPPLY PIPE

TO U3NSUMER

I

FROM UPfJER

CREST-

WEIR

I II

SPRING CATCHMENT

=-====L

DRAIN PIPE

J 9

-

7lt

,’ I

/ .’ .’ /

,,” ‘, /,/ ‘,‘,, 1

,-VENTIATION

DRAIN PIPE

1 cleaning pipe entrance basin

2 cleaning pipe collection basin

3 main valve

4 ball-valve for upper source

5 overflow entrance basin

6 averflow collection basin

7 baffle plate

8 strainer

9 climbing iron

10 aeration pipe

x = operating height of the

ball-valve + 30 cm

4-3.4.5 Outlet buildings

The

outlet

building

has

to prevent animals to enter the

inspection chamber.

Fig. 34 Simple outlet

Fig. 35 Siphon outlet

-II?&, a-- WI-

FAVMNT WlT+l Bb- -- -- ’ II

76

4-3.4.6 Common mistakes on spring catchments

Fig. 36

b

a)

permeable cover

b) leakage from pipe joints

cl covering over the spring is inadequate

d) no surface water drainage

e) chamber cover should be above ground

level

surface water can pollute

the spring water

f) position of overflow too high

1

g) position of oulet too high

t

obstruction to spring flow

J

h) no wire-mesh covering the overflow animals or dirt can

pollute the spring water

77

4.4

WATER POINT

4-4.1 GENERAL

Water points can

be

built anywhere if there is a small spring with a

supply of minimum one l/min. during the dry season and the possibility

to get at least 1 m difference in height from the catchment to the

drainage of the

storage

chamber.

The construction of a water point gives two main advantages:

- improvement

of

the quality of the water

-

hcxage

of water during the night for use in the day-time

If the spring supplies more than 15 l/min. in the dry season there is

no need for a storage chamber. A wash-basin into which the water enters

directly from the catchment can be built instead.

If the spring delivers less than 3 l/min. during part of the

year

only

a storage tank should be built, since a basin would never be filled, not

even during the night.

4-4.2 CONSTRUCTION OF A WATER POIWT

The

water

point itself normally consists of a storage chamber and a wash-

basin. Attention has to be given to provide a good foundation, especially

in swampy areas and on hill sides.

A proper drainage for 311 overflowing and used wash water has to be

installed. The design ,hould be such that all water runs to a certain pint,

from where a drainage trench with a good'slope will lead it quickly to a

nearby natural gutter.

A storage tank should be built if the spring gives less than 15 l/min.

in the dry season. Usually a wash-basin is connected to the storage tank

if the spring flow is above 3 l/min. minimum, below 3 l/min. minimum. The

water should be limited for drinking purposes only.

See figures 37 and 38.

Fig. 37 Small water point

= EFFECTIVE STORPGE VOLUME

(INTO WASH BASIN 1

PIPE

Fig. 38 Large water point

= EFFECTIVE STORAGE VOLUME

SPRING , SUPPLY PIPE .STORAGE TANK1 DISTRIBUTION PIPE

I , WASH .

CATCHMENT . . BASIN #

79

4-5

BARRAGE AND RIVER INTAKE

In the construction of a barrage its size, height and foundations are

determined by the stream, its bed and its embankments.

For our purposes the barrage does not retain water for storage and later

consumption (dry season, weekly variations), but is only built to assure

the supply. It should be perpendicular to the streambed. Special attention

is needed for the foundation to guard against:

- seepage

- washouts, leakages

- extensions of the wing-walls

- erosion of the river bed

4-5.1 DETERMINING MAGNITUDES FOR THE POSITION OF THE BARRAGE

a)

b)

cl

d)

4

f)

9)

i-4

i)

k)

above consumer

above populated areas (if necessary resettlement before the

construction work starts)

above farming areas, if not possible farming m,ust be stopped

along the stream

no cutting of trees in the catchment area, afforestation at

least 100 m to each side of the stream and on a length of

500 m to 1000 m

no watering place for cattle above the barrage

no laundry and no washing of cars above the barrage

good soil-bearing capacity

perpendicular to the stream bed

narrow stream bed which allows high speed to avoid standing

water behind the barrage and settlement

in stream bends the intake should always be at the outside

of the bend

Vl

= low speed

deposits of sand,

dirt, leaves etc.

V2

= high speed

no or little

settlements

4-5.2 DESIGN OF BARRAGES

The cross section of the

barrage

must be constructed in a way that the

overflowing water never separates from the barrage-surface because tklis

would cause heavy erosion on the foot of the barrage. (see Fig. 33 and 40)

The overflow area (Ab,) has to

be

equal to the river cross section (Ar)

by

high water or it will be calculated from the flow measurements.

Any standing water behind the barrage must be avoided. The speed of the

water before the barrage, in the spillway and along the sidegate should

be as high as possible.

Fig. 39 Cross section of a construction in concrete

IMPERMEABLE STRATUM

Fig. 40 Cross section of a construction in stone masonry

RMCABLE STRATUM

81

4-5.3

DESIGN OF INTAKES

The most suitable type of intake under these conditions are sidegates, the

entrance velocity Ventrance should bee 0.1 m/set, using a spillway as a

cleaner and regulator. The current along the gate helps to wash away leaves,

sticks and sand. The bottom of the spillway should be low enough to allow

dry season water to flow past the bottom of the intake. It is useful to

keep the deviation pipes which are used during construction so as to permit

maintenance and repairs by lowering the water. The gate with the strainer

which must be removable should be at least 5 cm, better more, below the

low water-level (LWL) . The gate should have a minimum height of 8 cm.

(see Fig. 41)

Fig. 41

Intake Construction

lntdke

chamber

GROUNO PLAN w 3

- SpillWdY

B

-.A

---em--

SECTION A -A

HWL . High

Udter

level

LifL - Low water level

sedimentation

cleaning pipe

SECTION B - B

intake chamber

retaining wall

or stone

82

4-6 WATER TREATMENT

4-6.1 GENERAL

It is obvious that

rural

water supplies should be designed to safeguard

the quality of the natural water selected. It should always be the policy

of a responsible engineer to restrict the use of water treatment under

rural conditions to only those cases where such treatment is absolutely

essential and where correct plant operation and maintenance can be secured

and supervised. The design engineer should also vigorously oppose the use

of treatment processes which the community concerned

can

ill-afford to

procure, operate and maintain with meagre financial resources. This

explains in part why a careful study, based on engineering and economic

analysis may have to be made to compare, in doubtful situations, the

relative merits of water treatment against those of long pipelines bringing

untreated water from distant springs, wells, etc. Experience shows that

whenever possible it is wise to make a large investment in order to

eliminate operational and maintenance problems.

(partly from "Water Supplies for Rural Areas and Small Communities"

WHO)

Furthermore, all the water supplies constructed in the Technical Section

of CD/SATA-Helvetas apply to the WHO Standards of untreated water (see

chapter 2-2). We consider this water quality as sufficient for any rural

water supply. In a future step chlorination can be introduced easily.

Treatment stations (sedimentation and

slow

sand filters) are

normally

calculated for con:inuous fl% over 24 hours in stage I (see 4-l.:').

4-6.2 SEDIMENTATION

4-6.2.1 General definition

Definition: Sedimentation is the removal of suspended particles heavier

than water by gravitation settling.

Natural existence: In the rainy season the erosion of the land by run-off

from rain-storms carries vast amounts of soil into streams and other water-

courses. Some of the eroded particles are heavy enough to settle when flood

waters subside, often to be picked up again and be redeposited further

downstream during successive floods until eventually reaching the ocean.

Influence on water supplies: such suspended particles prevent water supplies

from working continuously because they block pipes and filters, reduce the

capacity of storage tanks and the water quality. Therefore, these particles

have to be removed immediately after the catchment.

Methods of sedimentation:

The undesired suspended particles are removed from raw water by ser.iimentation

in a special tank. There are three kinds of sedimentation:

- Plain sedimentation: The impurities are separated from the suspending

fluid by gravitation and natural aggregation of the particles.

83

- Coagulation: Chemical substances are added to induce or hasten

------------I

aggregation and settling of finely suspended matter, colloidal

substances and large molecules.

- Chemical precipitation: Chemicals are added to precipitate dissolved

impurities out of solution by changing them into insoluble substances.

Plain sedimentation would be used where water contains much suspended

matter and particularly in warm climates, where higher temperatures

lower the viscosity of the water permitting thus more effective

sedimentation. The plain sedimentation requires less and simpler

maintenance than the other methods of sedimentation. Therefore, only

this method is employed by CD/SATA-Helvetas for rural water supplies in

Cameroon.

All the following remarks refer to plain sedimentation.

4-6.2.2 Design of sedimentation tanks

Sedimentation tanks are designed to reduce the velocity of the water flow

so as to permit suspended solids to settle out of the water by gravity.

The raw water (of rivers) contains impurities of three physical kinds:

- Particles large enough to be strained out of the water or which will

settle gravitationally in still water (sedimentation)

- Particles of microscopic or colloided form which will not settle in

still water and are too small to be strained out (filtration is

required to remove these substances)

- Substances held completely in solution, i.e. dissolved in the water

can be removed by chemical treatment only.

a) Factors affecting sedimentation efficiency:

7 mass density of suspended particle

- settling velocity

-----I!

shape density of suspended particle

mass density of the fluid

viscosity of the fluid

- drag force

---F-

shape of suspended particle

-- velocity of the fluid

I---- viscosity of the fluid

1 mass density of the fluid

- concentration of suspended solids in the fluid (settling hindered by

wall effect)

84

The only factor which is altered by plain sedimentation is the fluid

velocity. The smaller the size of the particles removed, the smaller

is the velocity of the fluid. The reduction in flow velocity needed

depends on the nature of th*: sediment and the required efficiency of

sedimentation (e.g. gritty, granitic

or

volcanic sediments being heavier,

need less flow velocity reduction to deposit them than fine lateritic

top-soils.

The efficiency depends also on design:

- inlet and outlet have to be constructed so that short-circni

prevented; ting is

- agitation of settled solids from the sludge zone has to be prevented.

Hence certain relations between length and depth are needed,

The required efficiency of a sedimentation-basin will depend on the need

to prevent blockage of the sand-filters (following). Further details have

to be determined by observation and resea:rch on similar existing

installations.

bl Calculation of the required dimensions

The dimensions of a sedimentation tank can be calculated from the surface

load and the period of detention. --

"Surface load" is the settling velocity of the particles in the water:

SL = Entity of water p er h m3 m

surface of tank =-

m2 x h h

In the reverse we can calculate the necessary surface as follows:

s, =

quantity of water_eer h

surface load m3/h

m/h

zz

m2

The capacity or volume of the basin can be calculated with the quantity

of water per hour and the period of detention:

v =

(quantity

of

water per h) x (period of detention)

m3

-xh =m3

h

The surface load and the period of detention varies widely because of the

kind of material to be retained, the stage of extension considered, and

the treatment added after passing the sedimentation (e.g. granitic and

volcanic soils bring heavier material than lateritic top-soils so the

surface load can be bigger and the period of detention shorter or vice-

versa).

85

The figures below,should only be taken as an approximate value:

SL =

surface Load max. =

0.6

m/h

(0.6 m/h is the settling velocity of' a silt grain with a diameter

of 0.01 mm)

t = periode of detention = 4 - 6 h

d = depth of tanks 1.50 m - 2.50 m (2.50 should be the maximum)

relation between length and depl-h 5:l up to 1O:l

The effect of sedimentation varies only with the surface load and not with

the depth of the tank.

The smaller the surface load the better the sedimentation.

Example:

quantity of water =

20

m3/h

surface load = 0.6 m/h

period of detention = 4h

relation between length and depth

5

:l

therefore:

necessary surface Sn

=

20.0

m3/h

0.6

m/h = 33.3 m2

====z====

capacity v =

20.0

m3/h x 4 h = 80 m3

---------

___------

depth

80.0

m3

=

33.3

m2

=

2.40

m

length = 5x2.40m = 12.0 m

.c

width

33.3

m2

=

12.0

m =

2.70

m

length =

12.00

m

====================== width =

2.70

m depth = 2.40 m

____-_--_------- ______----------

___------------- _------------_--

=

2.40m

I

LENGTH = .12.00 m I

86

i min = 3%

i = 8%

max

4-6.2.3 Construction details

Rectangular sedimentation tank s are most commonly used in Cameroon because

their construction is easier than that of circular tanks. Therefore, all

the following construction details are with reference to rectangular tanks.

a) Slope of the tank bottom

The cleaning of the sedimentation tank is much easier if its bottom has

a slope of min. 3%. I., 1

Inlet zone

Outlet

zone

b) Inlets and outlets

-

It is importantto achieve uniform flow of the water over the cross-section.

A straight inlet creates an equal straight flow to the outlet and a reduction

of the activ&capacity so that the efficiency is reduced.

Influence of 'water temperature on the operation of the sedimentation tank:

-__I

The operation of a sedimentation tank can be disturbed greatly by the

different temperatures of the inflow and the tank-water. Spring-water has

a constant temperature but stream-water temperature varies with sunshine

as well

as

with the change of day and night. Simplified the following pattern

appears in the sedimentation tank:

night (inflow cold) day (inflow warm) 8

inactive zone

therefore:

period of detention

shorter

reduced efficiency

These disturbances appear

already with very little differences in

temperature

about l/l0 to 2/10 OC between inflow and tank-water.

Well designed inlets

and

outlets reduce the influences of the water

temperature.

87

Fig. 42 Inlet: Variant 1

Vl (: 1.0 m/s V2 -c 0.3 m/s

OUTLET UXS

Fig. 43 Inlet: Variant 2

PREFABRICATED SLABS

VO s 1.0 m/s Vl e 1.0 m/s V2 c 0.3 m/s

A good working inlet shows a horizontal calm watersurface in the gutter

88

Fig. 44

Outlet

BAFFLEPLATE

/+ ,.’ ./

. ./

89

The crestweir is necessary

to have an equal overflow

along the weir

The outlet gutter should

always be reasonably deep

to avoid submerging the

crestweir because there is

a considerable slope of the

water surface in the gutter

4-6.3 SLOW SAM) FILTER

-----

Slow sand filters have been installed in many CD/SATA-Helvetas water

supplies with a stream or river as a source. This is due to the fact

that these filters can be easily maintained by the communities concerned

if they are properly instructed. Also, slow sand-filters show good results

in respect of water treatment, and their mode of action is quite simple

Definition: Slow sand filters are filters with a surface charge of

7,25 m3/m2 day (filter velocity 0,3 m/h) or less.

4-6.3.1 Mode of action

The raw water is led gently on the filter bed and percolates downwards.

Suspended matter in the raw water is deposited on the surface of the

filter bed. This layer of organic and inorganic material increases the

friction loss through the bed. The water level therefore rises gradually

until it reaches a predetermined value, not more than 100 cm. The bed

must then be taken out of service and cleaned.

The slow sand-filter does not act by a simple straining process. It works

by a combination of straining and bacteriological action of which the

latter is the more important. The mode of operation is complex. There is

no doubt that the purification of the water takes place not only at the

surface of the bed but for some distance below. Dr. A. Van de Vloed

distinguishes three zones of purification in the bed. lst, the surface

coating, 2nd the autotrophic zone existing a few millimeters below and

3rd the heterotrophic zone which extends some 30 cm into the bed.

1st stage = acts as an extremely fine-meshed strainer

2nd stage = decomposes plankton and the filtrate becomes oxidised by

chemical reaction

3rd stage = bacteriological filtration

In order to guarantee a good bacteriological filtration., attention should

be paid to achieving:

- favourable conditions for bacteriological reproduction and digestion

- slow filter velocity .

- raw water quality (pre-treated by sedimentation only, no chemical

additives like chlorine etc.)

- Minimal charge (steady flow) ca. 5 - 10% of the max. charge, in order

to keep the temperature on the filter steady and to avoid the growing

of seaweed.

90

4-6.3.2 Hydraulic system

From the hydraulic point of view a slow sand-filter and sedimentation

basin form an inseparable unit. Our main aim is to increase the service

time of a filter as much as possible. First, we treat the raw water by

sedimentation and secondly, we regulate the filter charge in such a way

that no unnecessary water is filtered. Flow into the sedimentation basin

should be determined as exactly as possible by water requirements. This

can be done by choosing different sizes of inlet pipes, or better, by

constructing a distribution chamber with a weir (measuring weir).

An adjustment of the inlet by throttle valves is not advisable; it may

cause blockages due to leaves etc. in the raw water.

There are two ways to control the filter:

a) In controlling the filter outlet: this can easily be done by

installation of a ball valve in the storage tank. A redu tion tee

fitted immediately before the ball valve guarantees a minimum

filter charge (steady flow = 5 - 10% of.the nominal charge).

A continuous circulation through the storage tank is ensured if

the storage tank overflow is installed at the opposite end of

the tank to the inlet.

b)

In controlling the sedimentation tank outlet: this can be done with

a similar installation as the one above. This solution has the

advantage of no extra water being retained in the filters. Therefore,

the growth of the algae is reduced and the service time of the filter

increases.

In Case a) and b) the excess water overflows in the sedimentation tank.

System a) : steadv flow A overflow

- t I

storage tanki-

I

L-,---l

control of filter outlet

System b)

steady flow

stor'age tank

control of filter inlet

/

91

4-6.3.3 Size and number of filters

The size of the filter1 bed can easily be calculated witn the follqwing

equation:

S =A v S = surface m2

Q = quantity of water per h or per day, m3/h or m3/day

v =

velocity below 7.25 m3/m2/day or 0.3 m/h

The ratio of length to width should be between 1 and 4.

The number of filter beds depends upon the quantity of water desired

as well as on the size of each bed. Nevertheless, it must be kept in

mind that the filters will have to be cleaned from time to time and

therefore, at least one additional stand-by bed must be available to

avoid interruption of the supply. If the two filters work together the

velocity will only be 0,15 m/h.

Example:

Quantity of water = 20m3/h

Filter velocity = 0,3m/h

Surface required = 20m3/h

0,3m/h

=

67m2

a) Chosen: 2 filter beds in action plus one stand-by

Hence the dimensions are as follows:

A per filter = 67m2 :

2

= 33,5m2

chosen width = 3m

- 33Am2

3m

=

11,2m

Total filter surface (incl. stand-by) = 3 x 3.0 x 11,2 = 100,8m2

b) Chosen: 3 filter beds in action plus one stand-by

Hence the dimensions are as follows:

A per filter = 67m2 : 3 = 22,5m2

chosen width = 2,5m

length = 22,5m2 =

2,5m 9,Om

Total filter surface (incl. stand-by) = 4 x 2,s x 9,0 = 9Om2

Preference may be given to solution b) because less surface will be

required, But cleaning a surface smaller than in a) will be more often

required. It is up to the engineer to decide which solution is most

adequate for the actual site circumstances.

92

4-6.3.4 Construction details

Fig. 45 Filter bed construction

1

mu. WATER Wm.

f

WATER

mu SAND LtvtL

*. . . ',. ;_- .

SAND B

0.~-1.oomm

. . . :

SScm. Or SIN0 CAN

BC

. .

RfMOVfO FOR CLfANlNG

min. SAM0 LtvLL

GRAVEL

5cm

B

S-lfmm

15cm

P

15-40mm

10 cm HO- lOmm

SLABS t* Scm

Fig. 46 Filter - long section

CONCRETE

SLAB OR

ClVERFUW LEVEL

SED. TANK

y / r’ /J

SLABS WITH SPACE 2 cm-l

93

Fig. 47 Filter - grou~$plan~

:!::,‘;’

:,:i I,,. , ‘( ,,

Fig. 48 Filter bottom

-

cross

section

. .

. . .

. . . ‘.

_, . * v

r.

..- _- . .

*. 3’

-L,

‘00

*-ie )e

: 06) I

,.’ ’

,:-

,’

Lmr

,’

-. . . . -..:

. . . : ., . . . . :

. . *

. . . .

.

.,. . .

‘. . : -*,.

. l * , :

-_.

. -.

..- ,. .*

- . :A.-;. -- * .

o’er0 b \--..*

@ I

l :e\.’

L CEMENT BLOCK

L SLABS

60&40/5cm

SPACE

2cm

94

OUTLET To THE

WEFwm ROOM

Fig. 49 Inlet gutter details

GROUND PLAN

ALU PROFILE -1.00 = MAX. SAND LEVEL

I

1

I i

CLEANING PiPE

SECTION A -A

Li ‘Lb-

MIN. WATER LEVEL

ml

w MAX. SAND LEVEL

- WOODEN BOARDS, TO BE REMOVED

ACCORDING TO THE SAND LEVEL

1” CLEANING PIPE

95

SECTION B-B

4-6.4 OTHER FILTER TYPES

4-6.4.1 Rapid gravity filter

Rapid gsavity-filters owe their name to the fact that the rate of flow

through them is about twenty times faster than through the slow sand-

filter (144 m3/m2/day for tropical areas only). Rapid filters work on

other principles than those of a slow sand-filter. There is no "Schmutz-

decke" film acting as a strainer on their surface; the sand bed is

cleaned regularly by forcing air and water upwards through the bed and

discharging the dirty wash water to waste; also the incoming water must

be chemically treated. The rapid gravity filter acts more as a "strainer

in depth" than the slow sand-filter but the process of water purification

is not entirely one of straining. As with the slow sand-filter, certain

complex biological and chemical changes are induced in the water as it

passes through the bed and these - as far as is known - are believed to

be the chief mode of action of the filter.

Rapid gravity-filters generally require too much maintenance and super-

vision to be adopted in rural areas.

Nevertheless a rapid gravity filter has been introduced in a treatment

station as an experiment. The reasons are the following:

It has been experienced in slow sand filters that they are blocked

after one to two weeks in rainy season because streams carry a lot of

suspended matter which cannot be settled out by the common plain

sedimentation. Due to this blockage filters need to be cleaned continuously

and the biological purification is disturbed. After cleaning, it takes

several days to build up the biological process again. In order to avoid

this continuous disturbance on the operation of slow sand filters a rapid

gravity filter has been preinstalled. It is expected that this rapid

gravity filter (v=60m3/day) will work as a strainer to the suspended matters

which have passed the sedimentation tank. While this rapid gravity filter

will require continuous cleaning the slow sand filters are expected to work

for months without blockage.

4-6.4.2 Pressure filter

Pressure filters are identical in bed construction and mode of action to

open rapid gravity-filters, except that they are contained in a steel

pressure vessel.

The advantage of pressure filters is that the pressure of water in the

mains (not above 75 m pressure) is not lost when the filter process takes

place, as is the case with an open rapid gravity plant (friction loss

1 m to 3 m).

96

4-6.5 TREATMENT STATION: LAY-OUT

Lay out for one sedimentation tank, two sand filters and one

storage tank (collection basin).

Fig. 50

Hydraulic system - ground plan

According to system bl in chapter 4-6.3.2

3TG?AGE TANK FILTER 1

FILTER 2

SEDIMENTATION TANK

(the cleaning pipes are not shown)

1 inlet to sedimentation tank

2 outlet of sedimentation tank

3 ball valve (depending on storage tank water level)

4 inlet

to

slow sand

filters

5 outlet of slow sand filters

6 inlet to storage

tank

(collection basin)

7 outlet of storage tank (supply to consumer)

0 overflow

I idle pipe

s steady flow

p& valve

See section in Fig. 51

97

SEDiM~NTATlON TANK

C I

7’ ,’

,

SLOW SAND FILTER OPERATION ROOM STORAGE TANK

Mt N. WATERLEVEL-

.

_ -.

rCllLICICL--.*->-1C&31-

,.. . .

. . . . :. . .

. . _ . . . *. _ . ..*

.’

*

1 inlet sedimentation tank

2 outlet sedimentation tank

3 ball valve

4 inlet slow sand filter

5 outlet slow sand filter

6 inlet storage tank

7 outlet storage tank

0 overflow

I idle pipe

S steady flow

C cleaning pipe

W valve

(Ground plan see Fig. 50)

4-7 STORAGE

4-7.1 GENERAL

The necessity of providing a storage tank is depending on the following

points:

a)

b)

In case the continuous supply of the source is sufficient to cover the

peak demand of the consumer, generally no storage tank is required. But

the supply pipe from the source to the consumer has to be designed for

peak consumption.

cl

Between the critical cases a) and b) are many other possible cases c).

/

4-7.2 CAPACITY OF A STORAGE TANK

A storage tank has to be provided in case the source's continuous supply

over a day is just sufficient to cover the daily demand of the consumer.

Because the hourly rate of consumption varies widely during the 24 hours

of a day water has to be stored during the time of lower consumption.

The maximum hourly consumption amounts up to 3 times the average

consumption. (compare chapter 3-2)

When designing a storage tank the first thing to consider is the capacity

which has to be provided. This depends mainly on the amount of supplied

water compared to the amount of consumed water. In some circumstances a

certain amount of water has to be stored additionally to cover normal

breakdowns or maintenance interruptions (e.g. for hospitals).

In the following the determination of the storage tank capacity for the

cases a) to

c) (as described above) are shown:

a)

Water has to be stored during time of lower consumption to be available

at the time of high consumption. Hence it follows that the required

storage capacity depends on the consumption by a village over a day.

The conditions vary in different parts of the world. Also local

customs cause local variations. A typical pattern of consumption in

a village in

a

rural area of the United Republic of Cameroon:

30 % of the day's supply between 6am and 8 am

10 % of the day's supply between 8am and 2 pm

35 % of the day's supply between 2pm and 5.30 pm

20,% of the day's supply during the other hours of day light

5 % of the day's supply between sunset and sunrise

A diagram of consumption has been drawn (Fig. 52) according to above

figures. In case ai;) of a continuous supply of the daily demand a

storage

volume of 40 % is required as it can be seen from the

diagram Fig. 52.

b) As described above in case b) generally no storage tank is required. In

practice the supply pipe from the source to the proposed storage tank for

stage II is calculated for a continuous supply of stage II (compare

example I, chapter 4-1.3). This capacity of the pipeline may be slightly

below the peak demand of stage I. Normally a small storage tank, in form

..,

I

of an interruption tank

, will only be constructed at the proposed site

for the storage tank stage II in case of hydraulic requirements (pressure

at taps).

99

Fig.

52 Water consumption

in

a

rural viilage with different

cases

of supply.

Lvvw coNsuMpTK)N

cl

As an example the case c) is shown in the diagram of colrJumption

(Fig.

521 where the source is able to supply the daie 3emand in 16 hours

As it can be seen from the diagram the required capacity of the storage

tank is about 23 % Icl + c2) of the daily consumption.

1.

1

60 .I.

ti i i iA

df*

n’ /

CASE a)

- diagram of hourly consumption

--- case a) the daily supply is

equal

to the daily consumption

---

case

b) the supply is equal to the peak consumption

. . . . . . . . . . . .

case

c) storage capacity required = cl + c2

Pig. 53 Daily water

consumption in Nqonzen water supply (grassland)

(an other example of case a)

x

II

100 I I I I I

no _ I

I

I I I

00 ., VW = \6+ v4 = 22st lBZ= 412

INFLOW EOUhL TO DAILY CONSUMPTION

70 . IF IN’FLOW WORE THAN OAILY CONSUMPTY)N

I- THE STORAGE VOtlJMC WILL BE REDUCED my/I f -

t i--

0

/

100

4-7.3 DESIGN OF STORAGE TANKS

The site for a storage tank should be chosen as close as possible to the

area of highest consumption.

The minimum water level in the reservoir should be between 20 - 80

m above

the area which will be supplied. If the level difference is

exceeding

80 - 100 m the system has to be divided in several pressure zones and the

necessary storage tanks or pressure reducing stations (interruption

chambers)

have to be provided for.

The water has to be protected against external influences. A good circulation

oL the water has to be ensured, due to the warm climate in tropical countries.

peration must be provided. Doors and windows have to be insectproof (mosquito

screens). There should be no entrance above the water level.

The operation chamber as well as the storage room have to be provided

with

good access for installation, checking, maintenance and repairs. During

cleaning work the supply must continue. Therefore two independent chambers

must each have an overflow capable of draining all the incoming water. Each

chamber has to be provided with a cleaning pipe to allow complete emptying

of the chamber. Independent chambers have to be provided with volumes above

30 m3.

Storage tanks are usually constructed rectangular in shape, but it might

be more economical to. construct masonry tanks in circular shape. Rectangular

tanks allow easy extension.

The water depth in the tanks should be as follows:

Volume Water depth in m

usual optimal

100 m3 2.00 - 2.50 2.50

100 - 200 m3 2.50 - 3.50 3.00

200 - 300 m3 3 .oo - 4.00 4.00

101

I,”

i’,

r3.g.

34

xorage

ianlc

construction

IR VENTILATION

-

iii/

,-

t

- INLE

4AU T (El/, WITH

_ VALVE 1

- *

1/1/i min ZOcm L/1 -.--‘.--” DlSTRiWTlON

4-8 DISTRIBUTION SYSTEM

The aim of the distribution system is to transport the water safely

from the main pipe to different places of consumption, such as stand-

pipes, wash-places, showerhouses, etc.

4-8.1 LAY-OUT OF THE DISTRIBUTION SYSTEM

When designing a distribution system of a water supply the following two

points have to be considered:

- the advantages and disadvantages of the different types of distribution

systems and

- the subdivision of the system into different pressure zones; if necessary.

4--8.1.1 Types of distribution systems

a) Branch system or dead-end system

In this system the distribution is done from a distribution main to the

different points of consumpti.on. The service pipes for individual supplies

are like branches of a tree. This system has the disadvantage of possibly

causing stagnant water in the dead-ends.

b) Gridiron system

This system is similar to the Branch system but here the dead-ends are

connected together with the result that the circulation is much better

and the possibility of stagnant water is reduced.

Of

dead-ends

103

In this system the distribution main is connected as a ring. The

advantages are considerable:

- good circulation of the water

- safe in case of breakdowns

- supply not interrupted in case of repairs

cl Ring system

.

4-8.1.2 Pressure zones

The distribution system must be divided in different pressure zones if

the difference in height between the lowest and the highest tap is mot-c-.

than 80 maters. The maximum water pressure at the tap is 60 to 80 IIJ..

from

the

source

d

4-8.1.3 Disposition of taps

Public standpipes and wash-places are installed according to the following

requirements:

a) population concentration: not more than 80 - 100 persons per tap;

no one should have to carry water mere

than

100 to 150 m

b) technical considerations: cleaning and aeration

8’

,“;!:

,, ,‘.

,, ., 2 ; ! ” y

1,

/,.A

104

4-8.2 PIPING MATERIAL

4-8.2.1 General

There are three requirements for a pipeline:

a) it must convey the quantity of water required

b) it must resist all external and internal forces

cl it must be durable

In order to &al with this subject adequately it is necessary to classify

pipelines into the following categories which may be defined as follows:

- "Trunk mains" are for bulk conveyance of water over long or short

distances from the source to selected focal points in the distribution

system. The following trunk main categories have to be distinguished by

their main functions:

a) "supply mainsW for the conveyance of water from the water source

(spring, river, lake) to the storage tank;

b) "distribution or service mains" are, as their name implies, the "street

mains" frorr. which individual house supplies are tapped;

cl "gravity mains" These last two classifications are made to specify

d) "pumping rains" the physical working principle of the supply.

- "ring main" is a special case of connecting two distribution mains

together. Ring mains are always of great value to a distribution system

because:

they tend to reduce the size of service main required

they maintain good pressure and flow within a distribution system

they give alternative means of feeding an area when shut downs for

repairs are necessary

they avoid stagnation of water at dead-end of main

. - "Service pipe" is the supply line, laid under ground frcm a main to

a village section quarter, a house, or a farm.

- "Plumbing pipes" are pipework within a building for the distribution

of water to the various appliances.

The following types of pipes are in use for the construction of mains:

Applicable Trunk main

cast iron pipes

---_-__.* .-.- -.- _

asbestos-cement pipes

.~

X

0

galvanized steel pipes

-----.- - ._.___. .._ ..__ _.

bitumen coated steel pipes

---

01

X

prestressed concrete pipes

,._.-.-.,. _

x =

applicable

X

plastic pipes (PVC + PE)

_I .-.

copper pipes

0

Service pipe

X

0

Plumbing pipe

0

x

X

0 =

applied in CD/SATA projects in Cameroon

1

= in special cases only

‘-

,‘”

4-8.2.2 Asbestos cement pipes

Asbestos pressure pipes are made exclusevely out of standard cement grades,

mainly Portland cement. The other raw material, asbestos, is a mineral of

magmatic origin, crystallized into very slender fibres (l/lO'OOO mm). Crude ,

asbestos fibre bundles are broken up into fine fibres between edge runner

rollers

and are then fed into a pulp mill. Here, about 10 - 15 parts of

asbestos are mixed with 85 - 90 parts of cement, with the addition of water.

Classification:

Asbestos pressure pipes are supplied in nominal sizes of 50 to 1'500 mm and

in pressure classes 5, 12, 20, 25 and 30 kg/cm2. I

The classes denote the test pressure in kg/cm2 of the tightness test in the

manufacturer's wcxks. The tightness test pressure is twice the working

pressure of the pipes.

Pipes are marked in the customary way, e.g. a pipe of 250 mm inside diameter

designed for a working pressure of 10 kg/cm bears the code:

Durabest 4

250,

class 20

Couplings are similarly coded, i.e.:

6

250,

class 20

All pipes are tested at twice the working pressure before leaving the factory.

Note:

Asbestos cement pipes in Cameroon are only used bitumen coated inside and

outside (compare chapter 2-4). They were the main type used for CD-SATA-

Helvetas projects until 1976. Now plastic pipes are applied more often due

to appearance of corrosion in AC pipes by aggressive water

4-8.2.3 Plastic pipes

Plastic pressure pipes and plastic pressure hoses offer considerable

advantages compared to pipes made of &her material, due to their great

resistance towards all known aggres,ive matter (see chapter 2-4.41, to

their light weight and their easy handling.

The raw material for plastic pressure pipes (e.g. Symadur pressure pipes)

is Polyvinylchlorid (PVC) in powder form.

The plastic pressure hoses (e.g. Symalit PE-hoses) are made of Polyethylene

(PE) mixed in powder form.

Much attention has to be paid tc an adequate fabrication, Plastic pipes for

the purpose of transporting drinking water

must

be fabricated according to

established regulations (e.g. in Germany: DIN 19'532). A well equipped

laboratory is required to examine the plastic material accordingly. Only

plastic: pipes marked with a test mark which guarantees adequate quality,

mu8t br! used for water supplies.

Of course, as we know from other material, we have to consider simple rules

to gain the required result. Care has to be taken when offloading, storing

or

laying the pipes.

106

);

1

1,

The following explanations are based on many years international and

factory internal experience.

Transport:

When transporting plastic pipes, it is essential that the bottom row of

pipes is supported along the entire length of the truck. The following

layers of pipes have to be piled up in such a way that sliding and

damaging of the pipes is avoided.

Stacking:

Symadur pressure pipes are resistant to influence of weather and corrosion.

The pipes can be stored outside for an unlimited time but/ it is advisable

to cover them during long stacking periods. The pipes must be stacked on

an even surface. The manufacturer advises to use wooden'batons at the base

and between.each layer. The sealing rings are to be stored in a cool and

dry place. They have to be protected against direct sun rays.

Trenching:

Large stones and rocks are pointsupports which may cause the pipe to break.

In case of rocky soil, the pipe has to be covered at least with a 15 cm

thick layer of stonefree material (e.g. sand?. In normal dry soil without

stones, it is not necessary to take special-precautions.

4-8.2.4

Steel pipes

Steel pipes are widely used because they are among the cheapest form of

service pipes and can sustain high pressure. They are supplied in straight

length of 6 m.

Note :

Only untreated pipes (black) can be bent to curves. If treated pipes are

bent to curves the protection may get cracks where in due course corrosion

will start.

Steel pipes may be supplied black (untreated) or galvanized, or bitumen

coated inside and out, or additionally sheathed on the exterior with glass

fibre cloth and a further coating of bituminous compound. They have screwed

ends and are connected by steel couplings. A great variety of special ones

are made, including flanges which are screwed on to the pipe ends.

Most

steel service pipes laid by water undertakings are galvanized.

Applicability on CD/SATA-Helvetas projects in URC:

Galvanized steel pipes-are applied mainly as plumbing pipes. But they are

also used on trunk mains and service pipes where the pipes have to be

exposed or where the earth cover is insufficient (e.g. crossing of streams,

rocks, roads, etc.).

107

4-0.2.5 Valves

There are three main reasons for including valves in a pipeline system:

- to alLow easy closing of a pipeline

- to control the flow

- to control the pressure

Types of valves in general:

applicable for

-

sluice valve (gate valve

plug valve

--.. . ---._--.-.--__ . . .._

butterfly valve

screw down plug valve *

(stopcock)

-.--. _.

non return valve

control valve

pressure reducing valve -

tight closure

X

x 1)

X

.-

flow control

-- --

."

X

pressure control

-

2)

-

2)

-

2)

- 2)

-

2)

X

a)

b)

cl

d)

4, b),

c) and d) are applied in CD/SATA-Helvetas projects in Cameroon

1) only with special equipment

2) pressure control functions only if water is flowing

a) Sl;ice valve (gate valve)

They are used to force a gate across a pipeline.

The gate is wedge shaped and is lowered into a

groove cast in the body of the valve.

Sluice valves which are left shut for a long time tend to stick and it

requires great force to lift the gate off the sealing. Similarly valves

which have been left open for a long time may not close properly because

of the collection of dirt in the gate groove which prevents proper insertion

of the gate. The difficulty with sticking valves and dirt on the gate groove

can be greatly reduced by operating valves regularly. If valves are not

operated for years they probably will not close. Serious difficulties could

arise if it became essential to close such a valve effectively.

The sluice valve is not the proper device for controlling the rate of flow

through a pipe because only the last 10 % travel of the gate towards

closure has any substantial effect on the flow rate (depending on the

pressure of the water in the pipeline).

108

b) Screw down plug valve (stopcock)

These are normally made only in smaller sizes. The body of the valve is

cast so that the water must pass through an orifice which is normally

arranged in the horizontal plan. A plug, a diaphragm or a jumper can then

be forced down on to this orifice by a screwed handle, thus shutting off

the water flow. The principle is used in all sorts of valves for shutting

off or controlling flow. The same principle applies to ball valves, to

pressure or flow control valves, to hydrant valves etc. When the size of

pipe (and therefore of orifice) is small then high pressure can be controlled.

'as is the case with the ordinary domestic tap. The defects of these particular

types of stopcocks are that their sealing need renewal from time to time if

they are frequently in use and that, even when wide open, they cause a

considerable loss of pressure head.

c) Non return valve

1(

'I

',

The universal.type of non-return valve consists of a flat disc set within

the pipeline and pivoted so that it is forced open when the flow of water

is in one direction and forced shut against a seating if the flow tries

to reverse. Another type of non-return valve is similar to a screw-down

valve except that there is no screwed handle. (It is possible to get a

combined stopcock and a non-return valve). In this type the plug or jumper

will be forced down on to the orifice by a spring or a weight.

:: '1

:!' Some water engineers are of the opinion'that if a non-return valve has to

', I,

';, ,, act very rarely, in a case of emergency the valve will either fail or

B :',

i, ,, function too slowly. Therefore, it is necessary to operate non-return valves

P',

i' , from time to time to keep them working properly.

!:

,I ',

fp; ,,','

v;,,: : 5'

q,;< ,~ _)

g;y,' I_,

$,‘ I

Li' ,a

<i

i':.,, ,,

/

C,.'. ,1:11

i:

,/ /:

$&a'.

$I". _ ,'

"," ,:. I

',1*,:

‘ ;,./ ',_I:i

ii',:', 109

;,,A ,(

~~~~~~~';.,:II;.:;",., ,, ',

$g@g,,;., ' A ;

;v" -L,, ,I I ,,, 7 ',

&,~;'$~,:

I'l

.'

,'

"

d) Control valve (e.g. ball valve)

Both flow control and pressure cont-rol valves are said to work on the same

principle since there can be no control of flow without control of pressure.

Whether flow or pressure is to be controlled the actual physical control

will have to be by destroying some of the pressure energy of the supply by

forcing the water to pass through a restriction. The over-riding control

of this restriction may be related to pressure or to flow.

The simplest type of controller is the ball-valve. A plug-valve, a butterfly

valve or a screw-down plug-valve which is controlled by a floating ball is

called a ball-valve (float-valve). This controls flow from a pipe according

to the water level in a tank. The rise of the float progressively closes

off the pipeline to diminish the flow for any given head.

4-8.3 DESIGN OF THE DISTBIBUTION SYSTEM

As a base for the calculation and the design of the distribution system

the following points should be known:

- The general lay-out of the water supply (see chapter 4-l)

- The lay-out of the distribution system (chapter 4-8.1)

- The ground plan of the system, including the location of

the consumers.

- the longitudinal section (with heights and slopes)

- the choice of the piping material.

4-8.3.1 Hvdraulic calculation of ninina

Whenever water flows in a piping system, there is a continuous loss of

pressure along the pipes in the direction of the flow. This loss of

pressure is due to friction between the moving water and the inner surface

of the pipes.

Experiments show that the head loss as a result of friction is

a) directly proportional to the length of piping

b) directly proportional to the roughness of the interior surface of

the pipe

c) approximately proportional to the square of the velocity

Calculations of friction-losses are actually determined by formulas

developed by Reynolds, Nikurades,Prandtl, mlebrook and Strickler.

For practical use we have tables and graphs or diagrams.

110

Tables: series of figures related to each other. Pay attention to:

headlines, dimensions, decimal points, remarks

Diagrams: lines or curves on a scaled rafter. Pay attention to:

dimensions, scales, interpolation

There are three ways to do the hydraulic calculation to determine the

dimensions of a piping system:

1) known: the quantity of water needed (e.g. the water flow at

peak consumption) and

the slope of the hydraulic! gradient of the pipeline

(friction loss).

To determine: The diameter of the pipe required.

2) known: The diameter

of

pipe avail.able and

the quantity IIf water needed (water flow).

To determine: The fricti,x loss (= the slope of the hydraulic gradient).

3) known: The diameter of the pipe line and

the slope of the hydraulic grad:'tint (= friction loss)

1'0 determine: The quantity of water flowing through the pipe line.

Peak consumption

The distribution sIpstem sh:l;; i be calculated for a peak consumption which

is equal to the sum of:

- the number of stand-pipe taps times 8 litres/min (d l/2"-tap)

- the number of wash place taps times 12 litres/min (4 3/4"-tap)

- the number of shower heads times 8 litres/min (4 l/2"-head)

or:

- 3 times the average supply in 24 hours (3 x Q24h)

The following diagrams will help you to calculate the friction loss for:

- Asbestos cement pipes (Fig. 56)

- Plastic pipes (Fig. 57)

- Galvanized steel pipes (Fig. 58)

111

‘.’ ‘, ’

c.

:_

,:._

Abbreviations for the following diagrams:

ND = Nominal diameter

D

= Outside diameter

d = Inside diameter

V

= Velocity of water

t = Thickness of the pipe

k = Roughness of the interior of

the pipes

Fig. 56 Diagram of friction loss in asbestos cement pipes

The nominal diameter = the inside diameter (ND = d)

k=

0105 mm

+H-+t+t

5 676

10 ai 30

QUANTITY OF WATER

( llmin 1

112

60

50

Lo

30

20

10%

7

5

L

3

2

I?&

lcm

Fig. 57 Diaqrdm of friction loss in pla-stic pipes (PVC and-E)

Nominal pressure = 10 at

k = 0,Ol mn

nominal

diameter outside

diameter

PE hoses

PVC pipes 50 mm

65 mm

80 mm

100 mm

125 mm

150 m-n

32 nun

40 mm

50 mm

63 mm

75 mm

90 mm

110 nnn

140 mm

160 mm

t

5,4 mln

6,8 mm

8,4 mm

3,cJ mm

3,6 mm

4,3 ml

5,3 mm

6,7 mm

7,7 nml

inside

diameter

21,2 mm

26,4 mm

33,2 mm

57,0 lnln

67,8 mm

81,4 mm

99,4 mm

126,6 mm

144,6 mm 1

Vmin

lOO%.a

I670 a P 30 Km0

QUANTITY OF WATER ( I lmin 1

80

60

50

40

30

20

10%

7

5

4

3

2

1%

113

Pipes according to DIN - Norm 2440

k

= 0,l mm

The nominal

diameter ND

3/Ofb or 10 mm

l/2"

or

15 mm

3/q" or 20 mm

1" or 25 mm

11/4" or 32 mm

1 l/2" or 40 mm

2" or 50 mm

21/2"

or

65 mm

3" or 80 ml

4" or 100 nun

the inside

diameter d

12,5 ma

16,0 mm

21,6 mm

27,2 mm

35,9 mm

41,8 mm

53,0 mm

68,8 nun

80,8 mm

105,3 mn

”

:

n

>

:; j ,,‘:e;, : :

1. ,‘.

Fig. $8

Diagram

of friction loss in galvanized steel pipes

B IOMnin 80 IlOI/min 200 300 500 XXII/mm

100

100*/w

10 80

w 60

!a 50

10

40

30 30

20 20

1 I ‘. , “” , 1 ,‘,I’ 1 %a

6 678 0 19 xl 200 3m 500 lea

QUANTI’TV OF WATER ( llmin 1

It is quite clear that a certain water velocity in the pipes is most

economical. The following table should give a general guideline:-

Trunk main-lines, supply main, pump discharge pipes

stage I v = 0.8 m/set stage II v = 1.S m/set - 2.0 m/set

Main-lines without house or stand-pipe connections

stage I v = 1.0 m/set

Distribution or service main

stage II v = 1.5 m/set

stage I v = 1.0 m/set stage II v = 1.8 m/set

4-8.3.2 Prevention of air pockets

The presence of air in a water main can cause serious blockages to the flow

wren when the main is of a large diameter.

Air pockets can be caused:

a) where the static head on the pipe is lower than 5 m

b) by high points in the pipeline and where the pressure in the pipeline

decreases (compared to the hydraulic gradient)

c) by operating a pipeline with insufficient means of aeration when

d) the flow capacity of the pipeline is

bigger

than the inflow

The minimum pressure in a pipeline should be at least 5 m.

Fig. 59

hydraulic gradient

at least 5m

correct

--

hydraulic gradient

diameter

Fig. 60 Longitudinal section showing desirable positions for air

valves on a length of pipeline

-. -. -, static

-. gxadient

-.-.-. -.-. -.-.-, -.- -.-.-

v desirable positions

for air valves

A low point with

cleaning pipe Arrows show the possible direction

of the air accumulation (-)

Point a: Air likely to accumulate because of lessening of hydraulic gradient

and steeper downgrade in direction of flow

Point b: Lessening of upgrade in direction of flow will cause accumulation

of air

Point c: Summit; large air valve for filling purposes will be required

hd * he

special case:

aeration in point e

because hd * he

Fig. 61 Hydraulic profile

wrong profile correct profiles

116

- It is obvious that air can collect tit high points in a main, but what

is not so obvious is that the high points are determined relative to the

hydraulic gradient existing on the main. (Fig. 60 shows an example). A

water main should not bc laid parallel to the hydraulic gradient (Fig. 61)

it should be laid with a rise or a fall (if possible). At the top of each

rise there must be an air release valve. An air valve must also be inserted

where a pipeline rises steepl?!, and then changes gradient so as to rise less

steeply. The valve should be ut the point of change of grade, even when

there is no definite high point on the main.

When filling a main, large valves for releasing air need to be fixed only at

those high points where it is obvious that air will have to emerge to permit

filling of the pipeline. Elsewnere, a smaller diameter air valve will suffice

Where long stretches of main exist with no distinct high point, one air

valve should be inserted at least every 1 to 1.5 km. This is especially

important when the pressure along the main is decreasing and thus allows air

to come out of solution from the water. On flat pipelines subjected to very

low heads, open-ended vertical pipes taken above the static gradient can be

used instead of air release valves, provided precautions are taken to pre-

vent pollution of water.(Compare with Fig. 62)

It should be kept in mind that air does not necessarily move forward with

the water but may move backward against the flow of water, slowly or

erratically (waterhammer).

- Before a pipeline can be filled with water , means must be provided for

releasing air from it. Once 'the pipe is full of water, however, any aperture

for release of air must be closed so that no water is lost. Ventilation on

high points should be open as long as air is escaping.

- When the outflow is bigger than the inflow it is obvious that the outlet

basin is empty all the time and therefore, the top of the outlet pipe will

not be covered with the required 20 cm of water. If this happens the out-

flowing water sucks air into the pipe and air bubbles will reduce the

capacity of the pipeline (more friction) more and more until the inflow

is bigger than the outflow. The water level in the basin will then increase

so that no air enters into the pipe. The capacity of the pipe will then

increase to be greater than the inflow and the process will repeat itself

again.

Note: Intermittent flow cannot occur with automatic air release valves,

but blockages to flow can happen with hand-operated air release valves

because air pockets can build up in a very short time.

Special case of air pocket which reduces the flow rate and can cause water-

hammer:

117

--.

correct

.

4-8.3.3

Prevention of vacuum

Vacuum can be caused:

- if the hydraulic gradient drops below the pipe axis

- if there is a closed valve in a main and the water from the continuous

main which is lower than the valve is drawn out for emptying purposes.

a) There is no doubt that in a well-planned supply system a vacuum caused

by

dropping of the hydraulic gradient below the pipe axis can be avoided.

But if a pipeline bursts at a low point a vacuum will occur at each of the

high points. Therefore, it is important to install automatic anti-vacuum

valves on all extreme high points, if there is a possibility of more than

5

m vacuum (and in steel pipes of large diameter, even less). Where the high

points have a very low head, open-ended vertical pipes taken above the

static gradient can be used instead of anti-vacuum valves, provided that

precautions are taken to prevent pollution of water (see Fig. 62).

b) Means to ventilate the pipeline should be provided after each main valve

to prevent building up of vacuum when the main valve is closed.

4-8.3.4 Air release valves and anti-vacuum valves

Fig. 62 Automatic valves

STATIC GRADIENT --

-.

Ventilation pipe min. b 1"

with return bend and sieve to

prevent pollution of water

caused by animals or dirt

-cleaning pipe

Open ended pipes taken above the static gradient can be used instead of

air release or anti vacuum valves.

ENTILATION

(with little

steady flow}

LARGE AIR VALVE ’ w

FOR fll.LlNC OF PIPE

I-iY - -- -LINE AT

HIGHPOINTS 0

- REGULATOF

s-

v DRAIN

118

AIR

L VALVE FOR

MAINTE NANCE

Fig. 63 Intermittent ventilatiofi

‘a)

stand

The ventilation valve has to be opened from time to time to ventilate the

pipe-line (prevention of air pockets)

(a) Also regularly used standpipes can prevent air pockets at high points.

Fig. 64 Anti vacuum valve

After closing the main valve the ventilation valve must be opened

(prevention of vacuum).

VENT11

VALVE

pipe

.ATION

CONNECTION

Note: The greatest care should be taken to keep all air valves well above

the highest possible ground-water level that can occur in any pit in which

they are sited. If this is not done, then polluted ground-water could enter

the main if it is emptied. The pit in which the air valve is sited should

. have a permanent drain leading to an open outfall which cannot be drowned.

This factor is an important one which will decide on the exact location of

the

air valve.

119

4-8.4

IMPLEMENTATION

4-8.4.1 Trench:z1g

The pipeline shoulci laid along the straightest route possible. Road

crossings should b<) ne at a right-angle to the road whenever possible.

Every length of main should k,: laid with a continuous rise of about 2%

to 5% to high points, so that air can be released through air valves, or

with a continuous fall to a low point, where a cleaning valve should be

fixed for emptying &at portion of the main. Flat lengths of pipelines,

or those laid parallel with the hydraulic gradient, should be avoided

since they may give air-lock problems.

Changes of direction should be made, whenever possible, by using:

- flexible joints, such as Viking Johnson coupling for steel pipes, or RK

CC

)ling for A/C pipes allowing gradual deflection

- r:iid joints using prefabricated, flanged or screwed bends.

TiZ”;.

.ed steel pipes should not be bent into curves because the internal

F‘ ctive coating may get cracks. It would be very difficult to remove

r 3 with screwed joints.

drtion of pipe into a coupling should preferably be done along the

itxis of pipes already laid, the shift being carried out after the pipe

has been inserted.

The maximum deflection recommended for asbestos pipe is $ = 50. (5O = 9 cm

offset/m length)

For other joints - according to the manufacturer

Note: the trench has to be wider at a bend than along a straight, to

allow space needed to complete the above pipe-laying instruction.

120

- DOTTohi DOTTOM

PLANNED TRCMH IOTTOW

COIIRCCT TOO HIGH

depends on:

I:',

- soil type and conditions _

. - cost considerations

The recommended economical width of trench at

at least a

= 60 cm.

121

pipe level is

In order to protect the pipe

against

damage from traffic and from weather

conditions, it is buried in the ground at a suitable depth. In the tropics

an earth cover of at leas‘- "3 cm (min. 60 cm) should be provided in order

-,_.-- -

to protect the pipes agai, t great variations of temperature, root growth

into flexible joints (between sealing rings and pipe) and against falling

trees. If the pipe is not buried, the water temperature increases and

provides excellent breeding conditions for microbes, and any tree falling

onto the pipeline may

cause

damage. When pipes are laid with more than

1.5 m to 1.8 m cover, a special investigation is called for to ensure that

they are strong I -ough to stand the earth pressure. If they are not the

remedy is to bed or fully surround the pipeline with concrete.

Trench depth like trench width also has an important bearing on laying

costs. All factors should, therefore, be considered very carefully before

excavating the trench.

Recommended depths for pressure lines in different situations

- through bush 100 cm (min 60 cm)

\

- along roads 100 cm

- underneath roads 150 cm

Fig. 66 Crossinq of main roads

normal back-filling The pipe should be laid The pipe should be laid

into a sand bed and be into a sand bed and be

covered with at least covered with approx. 20

20 cm sand. The remai- to 30 cm sand. An addi-

ning back-filling is tional concrete slab will

done normally. help to reduce the load

caused by traffic. The

remaining back-filling

is done normally.

Note :

.ling

Back-filling should always be completed in layers. Bulk back-fil

unsuitable as it results in excessive settling.

is

122

4-8.4.2 Laying of pipes

The pipe should be laid on firm ground or foundation in order to prevent

uneven settlement, which may damage pipe joints. In rocky soils,rocks and

stones should be cleared away from the bottom of the trenches for 15 cm

beyond the pipes and should be replaced by plain earth, sand, pea-size

gravel or concrete. A very large proportion of burst mains are caused

by pipes settling on large stones or rock points.

All tren roots between the surface and a depth of 1 m should be cut to

prevent damage to pipes from root growth (moving or squeezing of the pipe)

or by uprooted trees. This is very important if the pipes are joined with

rigid couplings because an uprooted tree can damage a lengthy section of

a rigidly joined pipeline.

Just before lowering pipes into the trench the pipes should be reinspected

(the first inspection having been done when the pipes were delivered and

stacked). This inspection should be concerned with finding cracks, blemishes,

punctures or other discontinuities of the external protection of all pipes.

At the same time - just before lowering them into the trench, the inside of

the pipes should be inspected for foreign bodies (like snakes, mice, gravel

or sand). The pipes, as well as their joining ends should be wiped and

cleaned.

A small depression should be dug out under the couplings or sockets so as

to allow an adequate support for the pipe over its entire length.

correct The pipe is supported

over its entire lenght.

wrong The pipe is supported

on two or more points

only (i.e. on the

couplings). Statically

it acts like a beam. When

back-filled the whole

wrong weight of the cover

rests on the pipe which

may cause it to fracture

in due course.

Moreover the couplings (rubber sealing rings) may be loaded unevenly and

leak.

123

Instructions for back-filling:

Back-filling onto a pipe requires as much care as preparing the trench.

The material must be soft and must not contain lumps of rock or large

stones. Once the pipe has been covered with 20 cm of suitable material

bulk filling of the remaining trench can be permitted. If there are a

lot of big stones that have been excavated it is not advisable to use them

for the bulk back-filling of the trench. If these stones are replaced by

soft material it will make it easier to excavate if the need arises !i.e.

repair-)-Initial back-filling (at least 20 cm above the top of the pipe)

should be done as soon as possibl c after the pipe has been laid to protect

the pipe from falling rocks, trees, flooding and cave-ins. Frovide a

continuous bed by carefully selecting the material for use under the

pipe and couplings and between the pipeline and the trench walls. A proper

back-filling between the pipeline and the trench walls is also important

to prevent a horizontal movement of the pipe wilich will occur if the pipe

is not laid in a straight Sine.

Water tamping may be used where drainage is good. Do not lift the pipe while

tamping.

Couplings or sockets are normally left exposed until the line has been tested.

After testing, the initial back-filling around the couplings should proceed

until each coupling has been covered by at least 30 cm of well-selected

material.

Fig. 67 Back-filling

1. Place soil up to l/2 external diameter.

2. Tamp soil under pipes and between pipeline

and trench wall at both side. Water

tamping may be used where drainage is good.

3. Place soil up to the top of the pipe.

124

4. Tamp

soil between

pipeline and trench wall

at both sides.

If the pipe trace has not been marked during construction it will later

5. Back-filling by hand until 20 cm over the

pipe. Tamp each 10 cm layer.

6. Bulk-filling of the remaining trench.

be difficult and sometimes very costly to find the pipe trace. It is

important that immediately after back-filling the pipe trace should be

marked by permanent signs to be able to follow the pipe if need arises

(e.g. building of new houses or roads).

A concrete peg which contains the following information may be the best way

to mark the pipe trace permanently:

a) Pipe material and diameter laid into the ground

b) The directions of the pipe trace

cl Continuous numeration in sequence of all concrete pegs.

Fig. 68 Examples of markinq peqs

i ,’

marks for pipe trace

direction

Asbestos cement pipe

gi 200 m

Peg No. 12

(continuous numeration)

a

m llem min

125

,

_,

Example for pipe sizes buried into the ground up to 4 100 mm

ipaicate

A piece of pipe embedded into a concrete

peg which is identical to the pipe laid

in the ground, e.g. a 1 l/4" galv. pipe

piece concreted into the peg means that

a 1 l/4" galv. pipeline is buried in the

ground.

The concrete pegs should generally

be

buried to one side of the pipe axis,

because:

a) In case of a burst pipeline some of the pegs may be removed while

looking for the leak and aeterwards they may not be correctly

replaced.

b) The material above the pipe initially will not be fully consolidated

and the pegs may sink with any subsidence and eventually get covered.

ACCORDING TO PIPETRACE

BUT NOT MORE THAN 300 m

0 4

-- -.

126

4-8.4.3 Thrust-blocks and anchoring

A pipe laid on sloping ground should be anchored frequently by having a

concrete anchor-block cast around it. Further thrust-blocks are

necessary at bends, tees, valves and tapers, and also at branch take-off

unless flanged joints are used. These blocks often have to be very large

and they must, of course, be well keyed into firm ground.

Note: The size of the thrust-block has to be decided on according to the

external forces occurring during testing of the pipeline, as the operating

pressure is lower than the testing pressure.

In soft soils, make sure that the concrete thrust-block is not firmly

attached to the line, or it may endanger line safety if the line beds

down unevenly.

Fig. 69 Thrust-blocks for changes of directions

required thrust-block area = R

soil-bearing power (T =LxW=A

ig, 73 Thrust forces P in metric tons at end closures:

(d

of pipe

mm

-

80

100

125

150

200

300

internal pressure p = kg/cm2

1

3 5 7.5

10 15

0.08 0.23 0.38 0.57 0.75 1.13

0.11

0.34 0.57 0.85 1.13 1.70

0.17 0.52 0.87 1.31 1.74 2.61

0.25 0.75 1.24 1.87 2.49 3.73

0.44 1.31

2.19

3.28 4.37 6.56

0.94 2.82 4.70 7.05 9.40 14

.lO

--

127

Factors for calculating thrust force R at bends and branches:

Bends:

90° 60° 450 300 221/2o 111/4o

Factors:

1.41 1.00 0.76 0.52 0.39 0.20

Branches factor = 0.70 (em&.rically drawn from experience

1

thrus

tforce '

R=

0,70

x P

R=P

R

= 1,41

x P

=

branches

factor

The thrust-block at changes of directions in the ground plan distributes

the forces so that the foundation pressure does not exceed the permissible

soil-bearing power.

Fig. 71 Thrust-blocks for changes of slopes

longitudinal section

This thrust block relies on its weight to withstand OCCIEing forces.

The following calculations are similar

to those for a thrust-block for

changes of directions.

Examples of calculation:

Example 1:

#I125 - $125

Thrust-block for a branch d 100 mm

Water pressure = 10 kg/cm2 II

/

Permissible soil-bearing power r= 0,75 kg/cm2 I

b 100

Out of Fig. 70: P = 1,13 tons, the factor for branches - 0,70

The required thrust-block area A = R = 0,70 x 1130 kg

r 0,75 kg/cm2 = 1060 cm2

========

Chosen: L = 40 cm

W = 30 cm with 30 x 40 cm = 12nO cm2

Example 2:

Thrust-block for a change of slope

Pipe B 150 mm

Water pressure = 7,5 kg/cm2

Specific weight of concrete = 2,4 t/m3

Out of Fig. 70: P = 1,87 tons, the factor for 45O = 0,76

The required thrust-block volume = & = 0,76 x I,87 t = o 5g m3

2,4 t/m3 I

I =======:

Chosen concrete thrust-block of 0,85 m x 0,85 m x 0,85 m (with 0,61 m3)

129

.,

d4.4

Pressure test of the pipeline

It is very important to test the pipeline before the trench is back-

filled to discover in time leaks and damages on the pipes (e.g. cracks).

After laying the pipes, the initial back-filling should be done as soon

as possible.

Fig. 72 Initial back-filling for the pressure test

This initial back-Eilling prevents a movement of the pipe duril:g the

testing and protects the pipe from falling stones, trees, etc. Before

the test can be started all the changes of directions and slopes have

to be secured according to chapter 4-8.4.3 by thrust-blocks and anchors.

Where lines cannot be tested under pressure in a single +zration, they

shall be tested in sections. In that case, the joints linking individual

test sections shall be tested for leaks by a final overall test.

The test pressure should be 20% to 50% higher than the service pressure

of the very pipe section. But at the lowest point of the section it

should never be higher than 1,2 times the nominal pressure of the

pipes.

Fig. 73 Testing bq pump

- end cap

pressure gauge

test apparatus

(hand pump)

Calibrated pressure gauges shall be used for testing, graduated to permit

correct reading to 0,l kg/cm2 pressure changes. It should be placed at

the lower end of the section.

For plastic pipes, the pressure should be constant if the pipe-line is

tight.

The limit for A/C pipes: The correct test pressure shall be restored every

half-how, Restoring is done

by

pumping water from the test apparatus

into the pipeline. The volume of water required to compensate the loss by

abeorbtion shall not exceed 0,05 l/m2 inner surface per hour.

Fig.

74 Testing by natural slope

For plastic pipes, there should be no loss of water in the transparent

water hose.

For A/C pipes, the refilled amount of water should not exceed 0,05 l/m2

inner surface per hour.

Notes:

- The testing pressure shall last for 15 minutes/100 m length of pipeline.

- The air at high-points has to be released during the filling of the

pipeline with water for the testing.

- The test procedure for asbestos cement pipes must take into account the

limited degree of water absorbed by the pipe raw material. Therefore, the

A/C-pipeline has to be filled with water under service pressure for at

least 24 hours before the main test can start.

131

4-8.4.5

Valve chambers

It is necessary to have valves at intervals along a pipeline which can

be used to control the flow of water. These valves are preferably

situated in a chamber built of concrete or cement blocks.

Fig. 75 Chambers with a depth up to 1,O m

c=

min 20 cm for pipes 4 50 and 80 1 depending on the length of

min 25 cm for pipes rd 100 and 150 1 the spanner to the open

screw of the joint

a ;: min 6Oun

or 2 x 6 + WTSIDE

& OF VALVE

t

b = min 60 or LENGTH

OF VALVE + 2 x 10 cm

Note: Length of valve always includes length of main valve and of

ventilation valve.

TEE PLUS min10 .

min 30

klel

I + min 30 4

OF VALVE

132

,I. ,_

Fig. 76 Chambers with a depth more than 1,O m

I

ir LENGTH 0F \(ALvE + 2

x iocm

L CLIMBING

Bi OF VALVE

0

@

1

a=

60 + c + OUTSIDE

.-

E 0 OF VALVE

IRONS

CLIMBING IRONS

Note: Length of valves always includes lengths of main valve and of

ventilation valve.

133

If a

pipe

passes through a wall, certain stresses from outside may affect

it and could damage the pipe. It is, therefore, very important to prevent

stresses by using constructional details as shown.

I i A

Rigid connection applicable for

cleaning pipes or pipeline inside

a building only

To make sure that there will

be no leak where the pipes

enter into the tank a single

flange fitting with one flange

in the middle of the wall is

very useful

expansion/contraction slip joints

134

6

Flexible connection applicable for

pipelines between different buildings

or for pipelines which are laid into

the ground and must be connected into

a tank (rigid)

At the end of PVC pipes a layer of

sand can be glued (with plastic glue).

This solution allows to connect this

pipe end directly to concrete

pipe-line

water

tank

pipe bridge

working space

during constr uction

To prevent the pipeline from breaking

by the settling down of the soil, a

pipe bridge has to be constructed

4-8.5 DISTRIBUTION BUILDINGS

The most important distribution buildings are

- the public standpipes from where the consumers carry water

- the public washplaces where the population washes clothes,

food crops or coffee

- and public shower houses.

Public standpipes and washplaces are installed according to the following

requirements:

a) Population concentration: Not more than 100 persons per tap

b) Distances: No one should have to carry water more than 100 to 150 m.

c) Technical consideration: Possible combination with high-points (aeration)

or low-points (cleaning pipe).

Public shower houses should be constructed in projects where enough water

is available and where no natural bathing facilities are at hand.

A standard rate is loo-150 persons per shower head.

No one should have to walk more than 500 m to the nearest shower house.

Constructional hint:

Every connection of a distribution building to the main pipe must have a

valve or a stop-cock so that repairs on the pipe branch can be made

without interruption of the main water supply.

4-8.5.1 Public standpipe

Fig. 77 Public standpipe

The standard designs in the

appendix show the construction

details and the list of materials

for the public standpipe (Fig. 77)

and the public fountain (Fig. 78).

135

Usually the public fountain is constructed on market places or in

centres of towns.

4-8.5.2 Public washplaces

Fig. 79 Public washplace in concrete construction

Fig. 80 Public washplace in stone masonry construction

The standard designs of Fig. 79 and

Fig. 80 are shown in the appendix

136

Fig. 81 Standpipe with washtable

Ground plan

.-

* -’

L.- TIE!

Section A- A

A

-.d

wash table

80 1 1.20

7 1

Fig. 82 Coffee wash-place

pipes

:hors

Section A-A

I

I L Section B-B

\1

rlevel 1 I

I-i--i- I

4-8.5.3 public shower housq

Fig. 83 Standard shower house

lb- roof

I

Ground plan (scale 1

:lOO)

Section A - A

Fig.

84 Public shower house with 8 heads combined with a fitting store

and 2 washplaces

l------------ ----------l

I I

I

t 4

I

I I

I I I I

pipe stacking

i I

I

f

I I

I

9 L -roof

fi

Ia

I

I 4 I

I i! I

I n, I

I

I I

L --- --- ---

1

-------A---

Ground plan

(scale

1:

100

1

138

4-9

WATER LIFTING

In rural areas, some villages may be situated in a way that enables them

to obtain their water supplies entirely by gravity. This is a big advantage

and should always

be

considered first when investigations for a water supply

start. It can be said that it is

always

safer to ccnstruct a water supply

which

works

by gravity, if this is possible, than one which requires

pumping. The gravity system needs less maintenance and keeps the running

cost low. The running cost and maintenance for pumps can be considerably

high for a commllnity which is financially weak. Nevertheless, in certain

cases it is inevitable to install pumps to obtain the necessary water.

4-9.1 TYPES OF PUMPS

There are two main types of pumps which are suitable for water supplies

- plunger pump (or piston pump)

- centrifugal pump ,

The following diagram shows the application of each one in relation to

discharge and delivery head.

Ii

m

P = Plunger pumps

C = Centrifugal pumps

The economical limit between

the application of plunger pumps

or centiifugal pumps lies at

the

ratio:

Q

(l/see) = 1

H (m)

Plunger pump:

The most common pump of this type is the reciprocating plunger pump in

which water is moved by the direct push of a plunger or piston which

reciprocates in a closed horizontal or vertical cylinder.

Centrifugal pump:

The pump-wheel turns with very high speed and centrifuges the

water

outwards producing the water pressure.

139

Summary:

Pumping systems

plunger pump

centrifugal pump for high discharges of water

other systems

4-9.2 HAND PUkPS

type of pumpr

application

deep well pump

(the pumping mechanism is

located inside the well)

for pumping-heights over 5m

(see chapter 4-9.2.1)

Wing pump

for suction-heights up

to 5 meters

hydraulic ram

(see chapter 4-9.4.1)

hydro pump

(see Fig. 90)

bucket and rope with

rope pulley

for wells

1

driving energy,

remarks

- hand pump

- driven by wind mill

- animal drive

... electrical or diesel

erlgi

ne

- hand pump

requires fast running

drives:

- electrical engine

- diesel engine

- petrol engine

- water turbine

self drive by water

(waterhammer)

- foot pump

- manpower

- animal drive

- diesel engine

4-9.2.1 Deep well pum&

The hand-operated pump can be usedin welis of any depth. In those which

have a suction lift of less than 5 m, the pump-cylinder is usually placed

above ground (shallow well pump, cominon pitcher pump). When the static

water lift is more than 5 m, the cylinder is attached to a drop-pipe and

placed in the well (deep well lift pump).

The deep well lift pump is one in which the driving mechanism (or power

head) is separated from the pumping mechanism (or cylinder). The deep well

operating p&p must be located directly'over the top of the water source,

with the cylinder either submerged or'w'ith'in the suction lift (ca. 5 m)

of the water. Since the water table level changes at different seasons of

the year,

it is best to have the cylinder

in

or very close to the water.

The experience has shown that this type of pump needs proper maintenance

and frequent checking. Specially the stuffing box, made of brass, is not

resistant to wear. The bolts for the pump head-connection have to be

tightened properly. Heavy use of the hand pump can produce wear on loose

bolts. Properly used, these pumps rarely require any expensive replacements,

and any work done on them can be carried out by relatively unskilled persons.

A well designed deep well lift pump is a simple and economical solut.ion to

- _----

lift water from a deep well.

;I,

Fiig, 85 Deep well

pump.

construction and maintenance needs

-

_ 1

1

J

Fig. 86 Deep well pump with

fly-wheel

This hand pump is also

suitable for other drives:

Wind mill, animal drive,

engines, etc.

DEUVEW (Un AND FORCE)

MAX TAPPIN r B.&P.

Fig. 87 Nomograph for hand pump discharge

Literature reference: 7 (see selected Bibliography)

4-9.2.2 Wing pump

Fig. 88

L

handle,

The wing pump is constructed

differently to the plunger pumps but

the working system is the same.

Applicable for suction heights up

to 5 meters only (with foot valve).

Without a foot valve, wing pumps

are only satisfactory for very

short suction lifts.

142

4-9.3 CENTRIFUGAL PUMPS

These pumps are often used because they are light, simple and need only

limited space for installation. Air vessels are normally not required.

Regulation is done by the use of throttle valves. The connection to fast

running engines is required.

Caution-if the water contains sand !

The dif,ferent types of construction:

- with vertical axle for installation in wells

- with horizontal axle for normal installation

- one or more stage units to meet high delivery heads

Mode of action:

In the centrifugal pump, energy is applied by a rapidly rotating impeller

in which kinetic energy is transformed into waterpressure. As a result

water is propelled out of the discharge opening.

4-9.3.1 Planning of centrifugal pump installations

It must be very clear that the planning of centrifugal pumping plants should

be done by an experienced engineer. The following explanations are not aimed

to give all the required information in this respect. For more detailed

information see "Planning of Centrifugal Pumping Plants" by Sulzer Brothers

Ltd, 8400 Winterthur/Switzerland, or other relevant literature.

II_ will always be necessary when designing a pumping system to involve the

manufacturer of the pump and the pump drive as early as possible in the

planning. 1

L

Pump characteristics:

Each centrifugal pump has a characteristic ratio between discharge,

delivery head and revolutions. This characteristic is shown in a curve

called characteristic line.

The characteristic line of a pump is calculated by the manufacturer and

checked with a test installation. H

There are pumps with steep and flat

characteristic lines:

- steep characteristic line: small

change of Q results big change of H

- flat characteristic line: Q changes

very much even if H is changed only

a little.

The head H as shown in the characteristic curves of centrifugal pumps is the

total or manometric head, i.e. the increase in pressure that takes place

between the suction and discharge branches of the pump, expressed in meters

liquid column.

The head losses in piping installations include all losses due to friction,

losses due to changes of direction of flow and sectional area, and any inlet

and outlet losses into and out of containers.

Velocity in suction pipe:

g! e 100 sun max. 1.0 m/see

6 a 100 mm max. 1.5 m/set

normally 0.6 m/set

Velocity in discharge pipe 1.5 m/set to 2.5 m/set. This veloci%y is quite

high but with this it is possible to keep lower the costs for fittings.

Required number of pumps:

Each pumping station needs at least two independent pumping sets capable

of providing the required delivery in order to ensure an adequate stand-by

facility. Also, the system should be capable of pumping the maximum

daily

requirement ideally in 16 hours , and always in less than 20 hours.

Parallel running of centrifugal pumps is never economical. The discharge

conditions have to be checked seriously if a second plant is installed to

run parallel to an existing one.

4-9.3.2 Pump drives

There are various ways of driving a pump. The choice is generally governed

by a community's financial resources. Always contact the manufacturer during

the planning stage. Look for a drive which is sold on the local market

(maintenance, repairs), if possible.

Water turbines:

A water turbine has the lowest running cost as a pump drive. Even though

the initial investment is quite high, this system is in the long run cheaper

than

other

drives.

The rotation of the turbine wheel or runner is caused by water flowing over

curved vanes fixed to the rim. The action of these blades is to change the

velocity of the water in magnitude and direction. The impulse given to the

wheel is entirely due to this change of velocity. A force causing rotation

results as the water passes over the vanes.

Turbines can be used in all cases where water is available in sufficient

quantity with a head of at least 1.0 m. It is essential to contact the

manufacturer in order to determine the correct type of turbine for a

specific project as early as possible.

Diesel engines:

The most common pump-drive is a diesel engine, as such an engine is quite

independent. It only requires gasoil and lubricants and these can be

transported to nearly any place.

In the diesel engine, air is compressed to a high pressure, hereby raising

its temperature to over 1OOOoC. Gasoil is in:jected by the injection pump

through the injection nozzles and ignites spontaneously. Diesel engines

are four stroke engines (some are two-stroke).

Diesel engines can be used to drive plunger as well as centrifugal pumps,

provided suitable transmissions are fitted. A diesel engine should have

about 25 % to 30 % more power than is required to drive the pump under

normal conditions. For exact determination of the engine it is necessary

to get in touch with both the engine and the pump manufacturer. It is

important to state in your enquiry the altitude above sea-level, because

the output of an engine decreases with increasing height.

Electric drive:

Electric drive is to be preferred if electricity is available at reasonable

cost. Electric motors are relatively low in original cost and are economical

to operate. Mains electricity supplies can rarely be used for our purposes.

t Therefore, this drive is not explained more detailed.

4-9.3.3 Pumping stations

Pumps are installed in a covered pumping station to protect them from rain

and bad weather. If the pump is driven by a diesel engine it is necessary

to provide adequate space for fuel storage. Fuel should,whenever possible,

be stored in a separate room planned for this purpose. The pumps as well

as the engines (electric or diesel) should be placed to allow easy access.

The height of the pump-basis should be about 70 cm above the floor. The

minimum distance between two pumps should be at least 80 cm.

Some more important points are:

- suction lift never

more

than 5.0 m

- install always a strainer with a non return foot valve in the suction

pipe

- the suction pipe and the reducers should be laid without any slope

to avoid air-pockets

- install always a valve before and after the pump (possibly throttle valves)

- the stuffing boxes of the pumps should be leaking always

- pumps with big manometric heads should be operated in the following way:

1. starting the pump

2. open the valve

3. running

4. close the valve

5. stop the pump

- the exhaust system of diesel drives should be properly installed. Ensure

good aeration and ventilation of the operation room

- Never run the pump without water! If possible a security switch should

be installed to avoid working of the pump without water.

L

145

4-9.3.4 Data needed by an enquirer

1) Arrangement or as per enclosed sketch No. .,...I.... altitude above sea

level . . . . . . . . . . . . . . . . m

2) Purpose of pump . . . . . . . . . . . . . . . . . ..I...................................

3) Duty of pump

a) Discharge in l/set . . . . . . . . . . . . . . . . . . . . . . . . . . . or cu.m/sec . . . . . . . . .

b) Manometric suction head .,........*..*........ m liquid column

c) Manometric head .,"........................... m liquid dolumn

(including manometric suction head under 3b)

4) Data for installation (only answer questions 4a and 4b if 3b and 3c

above cannot be answered)

a) Static or geodetic head:

Hd '90 = Height between pump centre line and upper water level . . . . . m

HS gee = Height between pump centre line and lower water level . . . . . m

H geo = Height between upper and lower water levels . . . . . . . . . . . . . . . m

H max

or

H' max = Height between lower water level and free outlet . . . . . . . . . . m

b) Piping data:

rd = Inside diameter of suction pipe . ..I......

L.5 = Total length of suction'pipe . . . . . . . . . . m

Number of bends in suction pipe . . . . . . . . . .

Inside diameter of strainer and foot valve . . . . . . . . . . mm

c) Supplementary information: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..*.........

..,..........~.......................................................

5) Water temperature

Specific gravity . . . . . . . . OC

Is pure water being handled? ..,.....*..................................

Has the water corrosive properties? . . . . . . . . . . . . . . . . . ..I................

Solid constituents, nature and quantity of mud, sand, quartz, etc. If

large foreign bodies are present in the liquid, state maximum diameter

of these . . . . . . . . . .

6) Drive

a) Electric motor drive:

Type of current: Direct, single or three-phase alternating current.

Frequency . . . . . . . . . . . . . . Hz (cycles/set)

Voltage .*............ volts

Is the installation subject to

dry,

damp, wet or dusty conditions I

or is there a fire explosion hazard? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- . . . . . .

i

146

~&:~~.‘,‘,,; . 1 “~ ‘/

b::. .,{‘, 1 .- ‘: %“’ I :-

II ,.,. .

i,~’

,: ,‘.I

b) Other drives:

I Petrol engine, Diesel engine, steam turbine . . . . . . . . . . . . . . . . . . . . .

: ;' If existent: Power N = . . . . . . . . . . Speed n = . . . . . . . . . . . . . . . . . . . r.p.m.

c) Belt drive:

'..

: , Driving pulley Diameter . . . . . . . . . . . . . . . . . . mm

Width . . . . . . . . . . . . . . . . . . mm

.I Speed . . . . . . . . . . . . . . . . . . r.p.m.

7) Service and economy

Is the pump to work in parallel with an existing unit and discharge

into the same system ? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

If so, was the existing pump supplied by us ? . . . . . . . . . . . . . . . . . . . . . .

Order No. . . . . . . . . . . . . . . . . . . . . . .

If of other manufacture, enclose characteristic curve of pump. IS the

pump to operate occasionally under conditions other than stated under

3a and 3b? If so, what are these conditions? . . . . . . . . . . . . . . . . . . . . . . .

Approximate number of working hours per year . . . . . . . . . . . . . . . . . . . . . . .

In case of electric drive, cost per kWh of electricity . . . . . . . ...*..

8) Information required for approximate calculation of pressure fluctuations .

in the piping

The following additional data is necessary for this purpose

a) For the working conditions at maximum discharge

- If the new pump is to discharge into a common pipe with an existing

pump or pumps, how great is the total maximum discharge quantity?

. . . . . . . . . . . . . . . l/set

Hmano would then be . . . . . . . . . . . . . . . m

b) Discharge pipe:

- Total length of the pipeline . . . . . . . . . . . . . . . m

- Mean inside diameter . . . . . . . . ..I.... IMU

- Static head at the pump . . . . . . . . . . . . . . . m

- Longitudinal cross-section of the pipeline, also showing vertical

elevations as per Sketch No. . . . . . . . . . . .

or

Drawing No. . . . . . . . . .

(If necessary indicate the various inside diameters)

- Is the pipe directly connected to a reservoir? . . . . . . . . . . ..I.....

- Is the pipe indirectly connected to a reservoir through a

reticulation network? . . . . . . . . . . . . . . . . . .

-

Is

water

continuously being tapped along the pipe, and if so,

how much? . . . . . . . . . . . . . ..I..

c) Existing equipment to counteract pressure fluctuations. These may be:

flywheels, air vessels, controlled non-return and discharge valves,

air injectors, surge tanks, etc. If any such device is available

please give brief particulars of its design, size, arrangement and

the experience acquired with it . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~..................................

d) Remarks:

147

4-9.4

OTHER PUMPING SYSTEMS

4-9.4.1 Hydraulic ram

A hydram is the best water lifting device, provided sufficient water flow

(drinking water) and head are available. Drinking water must be available

in sufficient quantity because it is also used as driving water.

Mode of action:

In the hydraulic ram (hydram), power is derived from water-hammer effect,

produced intentionally, The force of the water is captured in a chamber

where air is compressed by the sudden stopping of the main flow of water,

and released when the compressed air expands, pushing a small amount of

the water to a higher elevation than that from which it originally came.

The water not lifted to the higher level is wasted. Each compression

and decompression of the air in the chamber propels a definite quantity

of water up to a storage tank (reservoir).

There are two types of hydrams. Both types are in operation in North-West

and South-West Provinces of the United Republic of Cameroon.

The two types are supplied by:

- John Blake Limited, P.O. Box 43, Accrington Lancashire, England

- Schlumpf AG, Maschinenfabrik, 6312 Steinhausen, Switzerland

Installation:

- Blake; this hydram must be firmly bolted to a concrete base

- Schlumpf; this hydram must be firmly bolted to its drive pipe (no

concrete base). Only steel pipes should be used as drive pipes.

Ensure that the hydram is installed level. When a stop-valve is fitted on

the drive pipe close to the ram, the valve should be fixed in a horizontal

or oblique position to ensure that no air-pockets will form in the valve.

Note:

If a sluice valve is installed near a hydraulic ram it is necessary to fix

the valve with its horizontal spindle (level) or if a special valve with

an air tap is fixed the spindle should be at a 45O angle so that the air

tap in the crown of the valve would be in a vertical position, so as to

release any air which might accumulate there occasionally. If this point

is not taken into consideration air may accumulate in the crown of the

valve and this will influence the smooth operation of the ram or in some

cases the ram will either stop or fail to pump water.

148

Fig.

89 Hydraulic ram

A = airation of driving pipe

C = collection tank or sedimentation tank

R = hydraulic ram

St = storage tank

Qi = supply from source

0 =

over

flow

S = strainer at drive pipe

Ql = driving water

Ll = length of drive pipe

Hl = difference in elevation between ram and supply - power head

H2 = difference in elevation between ram and storage tank to which

water is to be elevated - pumping head

w = waste-water

Q2

= supply from ram to tank - possible daily consumption

L2 = length of supply pipe

D = distribution pipe

Given suitable circumstances - a situation similar to that shown in which

the supply of water is considerably in excess of the needs, and is situated

in a way that permits the

ram

to be located well below the supply - the

hydram can be an excellent solution to a pumping problem. It requires

practically no maintenance and will work 24 hours per day requiring

neither attention nor operating costs:

When the driving water is delivered by a stream, the water has to pass

a sedimentation tank in order to permit sand to settle out of the water.

Period of detention approx. 1 hour.

When writing to the manufacturer about ram sizes, the information in items

Ql, Ll, HI, Q2, L2, H2 is necessary.

Hl

Keep in mind ~2 = 1:4 to 1:8. The drive pipe should have a static pressure Hl

of max 15 m, if more, we need more stages.

(1:4 to 1:5, for rams

149

of the make "Blake") .

4-9.4.2 Hydro

pump

The hydro pump can be used in wells of depths up to 60 m.

Fig. 90

The

principle of the hydro pump

Discharge ---.,

valve closed L

The sleeve ----- -

retracts

Suction valve -

open

i

.

Discharge

A valve open

-- The sleeve

extends

+----- Suction valve

closed

Suction: The pedal goes up,

the sleeve retracts: water

is sucked into the stain-

less steel pump body.

Discharge: The pedal goes

down. Hydraulic pressure is

exerted in closed circuit on

the elastic sleeve which

expands and chases water to

the

surface.

The advantages of this pumping system are:

- the easy installation of the pump

- the simple maintenance (all wearing parts are located in the pump head

and are directly accessible).

Hydro pumps can be adapted

for other types of drive:

hrnd tyos

wlnd whwl lypa

I

Chapter 5: ADMINISTRATION OF PROJECTS

Table of contents page

5-1

5 - 1.1

5 - 1.2

TECHNICAL REPOKT

The aim of the technical report

Contents of the technical report

153

5-2

5 - 2.1

5 - 2.2'

EXECUTION OF PROJECT 156

Before starting a project 156

During the construction 156

5-3 COMPLETED PROJECT 156

5 - 3.1 Financial statement 156

5 - 3.2 Final report and handing-over file 157

5 - 3.3 Drawing of plans 157

5 - 3.4 Document file of a completed project 157

5-l TECHNICAL REPORT

5-1.1 THE AIM OF THE TECHNICAL REPORT

The technical report is an important document, necessary in the various

steps of planning and implementing water schemes or other constructions.

In the hands of the Ministry concerned, the technical report is the basic

tool for preparing the budget of the new financial year as well as for the

planning of the yearly activities. The technical report is required by the

engineer or the technician in order to plan and to start a project.

Foreign aid organizations interested in co-financing a project will find

all necessary information and details in the technical report.

The technical report must be well presented and should be attractive to

the reader. Each page should be numbered and clear reference to the various

chapters should be given.

5-1.2 CONTENTS OF THE TECHNICAL REPORT

Listed below, as a guide line for technicians and engineers, are the

main points that make up a technical report. Emphasis should be put on

the preliminary surveys of the sources, before drafting the technical

report (see chapter 3-4.1).

1. Introduction

Reasons for proposing the project (e.g. present water conditions)

Situation and actual infrastructure

Population and demographic development

Socio-economical aspects (here, detailed and clear information is

especially necessary)

Self help activities

Map of the country showing the situation of the village

2. Water budget

Available water and analysis

Water consumption, actual and future

Water balance

3. Project description

Hydraulic system (general lay-out, chapter 4-l)

Catchment

Sedimentation, other purification plants (e.g. slow sand filter)

Pumping station, interruption chamber

Storage tank, other tanks

Distribution

Construction methods, choice of material

4, Estimated cost

The estimated cost should be as accurate as possible. It is necessary to

indicate the size and quantity of material (cement, reinforcing iron,

pipes, etc.). If possible, include the inflation cost during the

estimated

construction time.

Cost in cash:

a) Buildings

Catchmant

Sedimentation tank (Or interruption tank)

Storage tank

Stand pipes, wash basins

Shower house & store

b) Hydraulic installations

Pipes (plastic, galvanized, asbestos, etc.)

Pump with driving engine (motor-pump)

c) Sundries (10 to 15 % of buildings & hydraulics)

Transport

Tools, lubricant, spare Parts

Contingencies

Cost in kind:

a) Community

Bush clearing, opening access roads - excavating & backfilling of trenches

and pits (foundations)

supply of stones, gravel, sand, wood and other material available locally

Organization of community work

b) CD Department / SATA-Helvetas

Survey, projecting & planning

Administration and supervision

Total cost of the project (= cash + kind)

cost per capita / actual & stage I

5. Proposed financing

Village contribution in Cash

Village contribution in kind

Government contribution in cash

(various grants)

CD / SATA-Helvetas in kind

Foreign aid in cash

10 %

20 %

40 %

100 %

154

6. Organization

of the project

information is given.

8. Final remark and recommendation

These remarks are meant to recommend

project.

The Project Committee:

organizes meetings & community work

organizes the supply of local material

collects the village cash contribution

prepares applications for grants (government & other)

Consultants to the Committee:

- the community development officer and the engineer are consultants

to the Conslittee

7. Maintenance of the project

Maintenance is one of the most important points to consider before planning

a water scheme. Please read with attention Chapter 6 where all important

in a summary the construction of the

The completed report will be signed by the engineer (or technician) and

by the CD-Officer of

the area.

Annexes to the technical

report

Map of the country indicating the situation of the village.

Plans of the village (lay-out) including all buildings and installations

to be constructed.

Hydraulic profile of a water supply.

155

5-2 EXECUTION OF PROJECT

5-2.1 BEFORE STARTING A PROJECT

A project should not start before it is approved by the Community Development

Department and by the local authorities.

It is necessary to have a clear picture of the financial sources as: dates

of instalment from external aid, confirmation of government grants, etc.

At least 50% of the village contribution should be paid to the project

account before starting the construction work.

It is necessary also:

- to have recruited all masons & labourers needed

- to have all tools, material & machines

ready

- to have completed the technica,4L report with execution plans

- to have prepared the list of m,'iterial to be ordered

5-2.2 DURING THE CONSTRUCTION !

Close supervision is necessary to build properly the different elements

of a construction project.

At the project site, daily reports must be made and a iog book with material

book must be kept regularly by the foreman.

Periodic reports have to be prepared by the engineer. These reports show

the progress of the work, the problems, the contact with the local population,

the financial situation and include a proposition of how the project will

continue.

When financial grants are given according to the progress of the construction,

d report and a financial statement are required in order to receive further

amounts (Progress Report).

5-3 COMPLETED PROJECT

5-3.1 FINANCIAL STATEMENT

As soon as the project has been completed a financial statement will be

handed over to the department concerned (Community Development or other

departments).

The statement will show clearly the cost in cash on one side and the cost

in kind on the other side for each partner involved in the project.

156

!+3.2

FZNAL REPORT AND HANDING-OVER FILE

A final report of the completed project will be handed over at the same

time as the financial statement to the CD department and to the Project

Committee.

The final report should isnclude the following:

- Technical report, technical details & plans of all constructions.

- A brief history of the project.

- Comments on the technical aspects (possibility of extension, lifetime

expectation of installations, output, special care) and on the expected

influence of the new construction an the villagers and their surroundings.

- Handing over note concerning the buildings & installations to the Project

--

Committee and a duty sheet to the caretaker. -

5-3.3 DRAWING OF PLANS

A complete set of execution plans for all constructed buildings and

installations of the project should be drawn. These plans must include

all modifications made during the construction.

A site plan (lay-out) of the project should be drawn to scale 1 : 1000,

2000 or 5000 and show all new buildings and hydraulic installations (air

valves, cleaning valves, etc.) and houses of the village with foot path.

5-3.4 DOCUMENT FILE OF A COMPLETED PROJECT

Technical report, estimates, calculations, instructions (pumps, turbines &

other engines).

Correspondence and receipts of material.

Minutes of meetings and opening addresses.

Repairs, possibilities of extension.

Final report with financial statement.

All situation and execution plans.

Chapter 6: MAINTENANCE OF RURAL WATER SUPPLIES

Table of contents

6-l MAINTENANCE GENERAL

6-2 MAINTENANCE-INSTRUCTIONS

6- 2.1 Maintenance of wells

6- 2.2 Maintenance of catchments

6-2.2.1 Maintenance of spring catchments

6-2.2.2 Maintenance of barrages and river intakes

6- 2.3 Maintenance of treatment stations

6-2.3.1 Maintenance of sedimentation tanks

6-2.3.2 Maintenance of slow sand filters

6- 2.4 Maintenance of storage tanks

6 - 2.5 Maintenance of water points

6- 2.6 Maintenance of distribution system

6 - 2.7 Maintenance of pumping stations

page

161

162

163

164

165

159

6-1 MAINTENANCE GENERAL

Once a water scheme is completed it is necessary to pay great attention to

its maintenance so as to ensure a continuous supply of drinking water of

good quality and sufficient quantity.

The completed construction of a water scheme has to fulfill all expected

hygienic and technical requirements. Therefore, an improperly maintained

water scheme can be a great danger to the entire population of a village

because everybody assumes that the water flowing from the tap is good

drinking water.

Water is one of the most important elements of your life.

WITHOUT WATER NO LIFE :

Organization of the maintenance:

Before the completed project is handed over to the villagers the maintenance

of the water supply should be organized taking the following points into

consideration:

- A water supply maintenance committee should be formed in the village

which takes the responsability of the completed project.

- A caretaker should be employed. He will carry out the entire maintenance

of the project as it is described in the following chapters.

- The engineer concerned is responsible to instruct the caretaker before

handing over the project.

- All financial matters and distribution of responsibilities for an efficient

maintenance should be regulated in advance.

6-2 MAINTENANCE-INSTRUCTIONS

6-2.1 MAINTEN.ANCE OF WELLS

Every week:

Control the cleanliness of the well, hand pump and surroundings. If necessary

arrange for cleaning work, to be carriedout by the population. The drainage

of waste water (overflow) is very important, to prevent any contamination of

the ground water.

Every month:

Grease or lubricate every hand pump (compare Fig. 85). With an engine-driven

pump, follow strictly the manufacterer's instructions regarding service and

maintenance.

Every

four months:

Check the construction and buildings and repair all damages. Minor repairs

should be done without delay as soon as they are disccvered.

All necessary maintenance work should be done regularly. If any problem

cannot be solved by yourself, contact the nearest Community Development

Office, which will give the necessary assistance in cooperation with the

community and local council concerned.

6-2.2 MAINTENANCE OF CATCHMENTS

6-2.2.1 Maintenance of spring catchments

Protective zone of the catchment area:

Do not permit clearing and cutting of trees from the catchment area but

maintain the fire boundaries (gaps) around the area (in the grassfield).

Weekly inspections are necessary, especially during the farming season.

Prevent any farming inside the catchment area, report people concerned to

the local authority or to the administration. Special attention must be

given to hair roots entering the catchment; if they are not removed they

can cause a blockage in a short time.

Spring catchment and inspection chamber:

Once a month the overflow and surface drainages have to be inspected and

the grass must be kept short. Water measurements should be taken whenever

possible. Additional checking is necessary after heavy rainfalls.

Two times a year (March and September) inspect and clear the collection and

inspection chambers if necessary. Clean and grease locks. Check up whether

there are any damage or cracks in slabs, chambers, pipes etc.

Miner repairs:

Carnage such as leaking pipes, cracked slabs etc. have to be repaired without

any delay as soon as they are discovered. If the supply has to be stopped

for necessary repairs the population has to be informed in advance.

Major repairs:

Repairs which require the attention of the engineer have to be reported as

soon as they are discovered.

Comments:

All necessary maintenance work should be done regularly. If any problem I

cannot be solved by yourself, contact the nearest Community Development

Office, which will give you the necessary assistance in cooperation with

the community and local council concerned.

2 Maintenance of barrages and river intakes

Inspections:

Weekly: inspect dam, especially the spillway and intake. Check water quality.

If unusual contamination is observed find its cause (farming,

fertilizer, washing, fishponds, latrines etc.)

162

Monthly: inspect the overflow, check if there are any cracks or other

damage.

Minor repairs:

Minor repairs, once a fault is discovered, have to be done without any

delay.

Major repairs:

Repairs which require the attention of the engineer have to be reported as

soon as they are discovered, to prevent waste of water, contamination and

further damage.

6-2.3 MAINTENANCE OF TREATMENT STATIONS

6-2.3.1 Maintenance of sedimentation tanks

Inspections:

Monthly: clean and drain the tank. Keep installations, overflow, vent

holes and drains clean. Cut the grass arount the entrances.

Grease doors, locks, valves etc.

Twice a year: general check up of the buildings for damages such as cracks

or

leakages.

Minor repairs:

Minor repairs, once a fault is discovered, have to be done without any delay

to prevent waste of water and contamination.

Major repairs:

Repairs which require the attention of the engineer have to be reported as

soon as they are discovered, to prevent waste of water, contamination and

further damage.

6-2.3.2 Maintenance of slow sand filters_

Cleaning of the filter:

If a filter requires cleaning, the water has to be drained first. Then 1 cm

to 2 cm of the sand surface must be carefully scraped off. When the sand-bed

requires cleaning again a further layer of 1 cm to 2 cm of sand is removed

from the surface. This process is repeated until the minimum thickness for

efficient filtering of about 45 cm is reached. This level is marked in every

filter. After each cleaning the filter is returned to service. Though the

flow of water is reduced at first and the effluent is not connected to the

supply until it shows that it is properly purified after an interval of about

one to two weeks. The intervals for cleaning will depend on the amount of

water which passes through the filter as well as on the contamination. It

might be necessary in some areas to clean the filters every 3 to 4 weeks and

in others every 8 to 12 weeks.

163

If the sand-bed has reached the minimum thickness it is necessary to wash out

all the sand removed previously as well as the remaining sand in the filter.

After this it will take at least

2

weeks until water from this filter can be

used again for drinking.

Washing of contaminated sand:

Is is absolutely essential to stir the sand in such a way that all contami-

nation is washed out. To check if the sand is clean , take a hand-full and rub

it between your hands, if there is any sign of dirt on your hands the sand

is not yet clean enough.

The above should be understood as a general guideline. All instructions given

by the engineer for each project mhould be followed strictly.

Engineers in Cameroon are presently testing special sand wash places. Once the

results are available, a standard design could be worked out.

General inspection:

Twice a month: Inspect the filter plant, keep installations, overflows and

drains clean. Cut the grass around the entrance.

Twice a year: General check up of buildings for damages (cracks or leakages).

Minor repairs, once a fault is discovered, have to be done without any delay

to prevent waste of water or contamination,

Major repairs, requiring the attention of the engineer, have to be reported

as soon as a fault is discovered, to prevent waste of water, contamination

and further damage.

6-2.4 MAINTENANCE OF STORAGE TANKS

Inspections:

Monthly: Clear the surroundings. Keep vents, drains, etc. clean. Check the

water quality and for possible contamination. Check installation

(valves), look for leaks.

Twice a year: Clean the storage-tank, look for damages on the buildings,

cracks, leakages, plastering, installation.

Minor repairs:

Once a fault is discovered, repairs have to be done without delay to prevent

waste of water or contamination.

Major repairs:

Repairs which require the attention of the engineer have to be reported as

soon as a fault is discovered, to prevent waste of water, contamination and

further damage.

164

6-2.5 MAINTENANCE OF WATER POINTS

. _---

Maintenance of the spring catchment: see chapter 6-3.1

Weekly; clean wash-basin, if any

Monthly: clear the surroundings, cut grass. Keep air vents, drain, etc.

clean, check quality of water and for possible contamination.

At least twice a year: clean the storage-chamber, look for damages such

as cracks.

Important: Greatest attention must be given to the drainage.

Minor repairs, once a fault is discovered, have to be done without any delay

to prevent waste of water or contamination.

6-2.6 MAINTENANCE OF DISTRIBUTION SYSTEM

Stand pipes, wash places and shower houses:

Daily: Cleaning by the consumer. Special care should be given to the drain

pipe.

Weekly: General check up and special cleaning.

Monthly: Cut the grass if necessary.

Leaking taps have to be repaired immediately to avoid loss of water.

Soakaways don't need much maintenance. In case they are blocked by dirt they

have to be cleaned immediately.

Valve chambers:

Twice a year: Inspect and clean them. Any broken slab should be replaced.

Repairs have to be done without delay once a fault is discovered. All valves

should be closed and opened during these inspections.

6-2.7 MAINTENANCE OF PUMPING STATIONS

Pump and drive:

The manufacturer's maintenance instructions have to be strictly followed.

A special instruction manual for each pumping station regarding maintenance

can be made available (from the appropriate engineer).

Buildings:

Monthly:

Check installation

for

correct functioning (valves or stopcocks).

Look for leakages. Paint the installation, grease locks, etc. Check

that

overflows and drains are clear.

Chapter 7: SELECTED BIBLIOGRAPHY

1. - Hand Dug Wells and Their Construction by Watt, S. and Wood, W-E.,

1977, ISBN 0.903031.27.2 (f 3.95)

2.

- Hand Pump Maintenance in the Context of Community Well Projects.

Pacey, A., 1977, ISBN 0.903031.44.2 (E 1.25)

3.

- Water for the Thousand Millions, by Pacey, A., 1977,

ISBN 0.08.021805.9 (f 2.50)

4.

- Water Treatment and Sanitation by Mann, H.T., 1976, ISBN 0.903031.23X

(f

2.00)

5.

- Water, Wastes and Health in Hot Climates by Feachem, R., et al.,

1977, ISBN 0.471.99.4103 (f 10.75)

Note: All titles above from: Intermediate Technology Publications Ltd.,

9 King Street, London WC2E EHN, U.K.

6.

- Slow Sand Filtration for Community Water Supply in Developing

Countries by Dijk, J.C. van, Technical Paper No. 11, 1978 (US$ 10)

7.

- Hand Pumps by McJunkin, E.F., Technical Paper No. 10, 1977 (US$ 10)

8.

- Water Supply for Rural Areas and Small Communities by Wagner & Lanoix,

1959, Monograph No. 42

9. - Typical Designs for Engineering Components in Rural Water Supply,

published by WHO Regional Publication South East Asia Series, World

Health House, Indrapratha Estate, Ring Road, New Dehli 110 002, India

Note: All titles from: WHO International Reference Centre for Community

Water Supply, P.G. Box 140, 2260 AC Leidschendam, The Netherlands

10. - Shallow Wells, Report of a Well Digging Project in Tanzania, 1978,

(approx. US$ 18)

11. - Small Water Supplies by Ross Institute, 1978 (approx. US$ 4.50)

Note: Both titles from: TOOL Foundation, Communications Collective,

Mauritskade bla, 1092 AD, Amsterdam, The Netherlands

12. - Handpumps for Village Wells by Spangler, C.D., VITA

(US$ 1.95)

13. - Using Water Ressources, VITA 1977, No. 38 (US$ 5.50)

1975,

No.

28,

Note: Both titles from: VITA, Volunteers in Technical Assistance,

3706 Rhode Island Ave., Mt. Rainier, Maryland 20822, U.S.A.

167

14. - Water and Waste Water Disposal, Volume II, by Fair & Geyer,

1968, Wiley, New York

15.

- Rural Water Supply and Sanitation by Wright, F.B., 1977, Krieger,

New York

16. - Taschenbuch der Wasserversorgung by Mutschmann-Stimmelmayr, 1973,

Stuttgart, Germany

All titles may also be ordered through: SCAT, Varnbiielstrasse 14,

CH-9000 St. Gall, Switzerland

168

Chapter 8: INDEX OF KEY WORDS

A

B

C

I

Administration of projects

,Aggressivity of water

Air pockets, prevention of...

Analysis of

water

Anchoring of pipe line

Asbestos cement pipes

aggressivity towards

AC-pipes

friction loss in AC-pipes

pressure test of AC-pipes

prevention of corrosion

Back-filling of trenches 124

Bacteriological field test

40

Bacteriological standards for drinking water 19

Barrage

80, 162

Bibliography

167

Calculation of piping

Carbon dioxide (CO2)

Cement products

aggressivity towards cement

products

prevention of corrosion

Centrifugal pumps

Characteristics of water

Chemical

analysis of water

Chemical standards for.drinking

water

Chlorination

of

water

Climatic pattern

Coffee

washplace

Coliform bacterial count

Completed project

Connection details

Consumption

of

water

peak eonmumption.

specific consumption

Corrosion, prevention of...

169

151

22

115

40

127

106

24

112

130

27

110

23

24

26

143

15

41

20

6

137

19, 40

156

134

111

34

26

0 Daily water consumption

Deep well pump

Degree of hardness

Distribution buildings

Distribution system

type of distribution systems

design of the distribution system

maintenance of the...

Drainage in

Cameroon

Drinking water standards

E

Execution of project

F Field test

Field work

Filtration

Final report

Flow measurement

Fountain, public...

Friction loss in pipes

. ..diagrams

0 Galvanized steel pipes

friction loss in galvanized steel pipes

prevention of corrosion

Gravity, supply by...

Ground water

supply of ground water

H

Hand pumps

Hardness of water

Head loss in pipes

Hydraulical calculation of piping

Hydraulic ram

Hydrology

hydrologic cycle

Hydr0 pump

'I Infiltration

Inspection chamber

Intakes

34

141

25

135

103

110

165

14

19

156

40

33

90, 96

157

35

136

110

112 - 114

107

114

28

49

17

50

140

25

112 -

110

148

3

5

150

13

73

82

12

114

K

L

M

N

0

P

Laying of pipes

Lay-out of water supplies

lay-out in stages

lay-out of distribution

Location of water sources

Maintenance of rural water supplies

Marking of pipeline

system

Measuring of water quantities

MPN Index (coliform)

. ..field test

Organization

. ..of maintenance

. ..of project

Outlet building

Peak consumption 111

PH - value 22

Pipes

pipe connections to buildings

piping material

laying of pipes

Plastic pipes

friction loss in plastic pipes

prevention of corrosion

Plunger pump

Pressure test of the pipeline

Pressure zones

Project administration

Pumps, types of pumps

maintenance of pumping stations

pump drives

Quantities

of

water

measurements

,..of spring water

171

35

65

123

49

50

103, 51

35

159

125

35

19

40

161

155

76, 89

134

105

123

106

113

29

139

130

104

151

139

165

144

R

s

t

U

V

Rainfall

intensity of rainfall

quantity of rainfall

tables of monthly rainfall

Rain water storage

Rectangular weir

River intake

Run-off

Sedimentation

Service life

Shower house, public...

Slow sand filter

Specific consumption

Spring

location of spring

spring catchment

Stages, design in stages

Standards for drinking water

Standbipe

. ..with wash table

Steelpipes

Storage, storagetank

Stream

. . . catchment

Technical report

Testing the pipe

Thompson weir

Thrust-blocks

line

Treatment of water

lay-out of treatment station:

maintenance of treatment station

Trenching

Vacuum, prevention of...

Vt31&3

valve chambers

6

12

6

11

50

38

80

13

83, 163

51

138

90, 163

34

17, 65

35, 49, 66

67, 162

51

19

135

137

107

99, 164

18, 49

80, 162

153

130

37

127

83

97

163

120

118

108, 118

132

172

W Washplace, public...

Coffee washplace

Water

aggressivity of water

analysis

of

water

characteristics of water

ground

water

standards for drinking water

Water lifting

Water point

Water sources

location of water source

Water treatment 83

Wells 55

handpumps for wells 140

maintenance of wells 161

136

137

22

40

15

17

19

139

78, 165

17

35

Appendix: NORM PLANS AND SCHEME PLANS

Norm plan No. Title of plan

Scheme plan No.

Public stand pipe

Public wash place (in concrete construction)

Public wash place (in masonry construction)

Public:fountain (in masonry construction)

Interruption chamber with ball valve

Water point (in masonry construction)

7 Plumbing scheme of single storage tank

8 Plumbing scheme of double storage tank

Project plans as examples

Mankaha Bafut Water Supply (Situation plan)

Mankaha Bafut Water Supply (Hydraulic Profile)

[ 150m,n

SECTION B-B

SECTION A- A

SOAKAWAY

CEYE”T 1 N&o

STD”ES IO In’

YND Ollm’

LIST OF MATERIALS

STAND PIPE

EISNT 5 8165

WCLDCD WESN 26 I 46c.m

RODS 0 6mm SOm

Pm @ lmrn oN~y-Q----JDN = 1.45m

2rm. 0 6mm 1.2om

?m. ’ 6- t2p-J. : lm77m

16

4M 0 cmm IO 10 3 I

130 1.5Dm

am 0

6mm 10 = OJOrn

AC 50 4Om 1 PIECE

G.I. 4’ 0.25m

1 PIECE. TAP 4’ 1 4’or v

6.1.

SOUKET

Y 1. 0.I. ELEW u 1 *’ nr I’

STOKf5 5m’

SANII lm’

eMoN BLOCKS 6~ 16 a 20s4Dom

r -

--- L-J . z .-.

-----T

e+

L- -

&!!

1s 1 50 1 IS

I

51 SLOPE

---5

LIST OF MATERIALS

WASH PLACE

CfMfNT - 15 BAGS

SAND - 2m’

GRAVEL - 2.5d

STONES 2.5,x*

G.I. 4’ THREADEO WTN ENDS I PIF.GE(OR V,‘)

6.1. a’ dOCrn 4 PlEOES

I

-3.1. 2’

50cm WITH S0cKfT 1 PIECE

G.I. 2’ 3Ocm TNREAOED ONE EN0 1 PIfCL

“ TAP w 1 *I?? e

SCCKETC I # , ”

I

ELKlwtl , 1,

WELDED MESH 1”s 210 I 0.70m’

Zno 195 I 0.75 In’

I

1 no 0.35 .s 0.25 m*

AC 100 4m

RODS lo-. I em ,,& . O.,sn

Tn.. ,6nn Y” 10

166 , . IWIn

SOAKAWAV

CWNT -

15

l&S

R005;

SAN0

- id #‘mm 141

- ---~---~~-~-- -~

SECTION B-B

SECTION A- A

/2D!lDj 40 !2G! ,;,‘, j2D’ 20000 360

LIST OF MATERIALS

mxoE0 WLIll mN 5LM5

A.c.100 4m

5mrvlr 1011'

5GND 414

SOAUAWAV

CEnaY 4ilhc5

a05 ~~54Nl

l A9 &?w

WELaD YW roll LlITMNOE SUI 451 lW*m

5rom 12d

YIQ 1Rl'

-

SECTION A-A

--

30 45

SECT&

I

B- Ei

30

::

N

I

W",W.JAY

I - -0m uA5ONRY

200

SECTIOiJ C-C

ORAIM PIPE -

Ii ’

’ ” ’

!4

I t/!-l

1 - hl 1 1 I

t

LIST OF MATERIALS

FOUNTAIN

CEMENT 15 BAGS

G.I. PIPES Y 3Ocm 9 PIECES

G.I. SOCKETS +t’ 4 y

iAPs Y’ 4 I

G.I. TEES w a’$2 ”

G. I. TEE ** Y&1 y

G.I. NIPPLES @I’

2

c

G.I. PIPES fi’ 25cm 4 ,

G.I. PIPE r 115om 1 Y

0.1. ELBOW REO 18’-++’

G.I. PIPE N’min 250cm

A.C. PIPE II 6Omm 4m

SOAKAWAY

CEMENT 4 BAGS

ROOS 0 6mm 54m

17no $6mm ‘9 140 ‘g = 160cm.

10

14no 0 6mm c 10

170 -) = 190cm

WELDED MESH EOR ENTRANCE SLAB 45x 105 cm

STONES 12 ml

SAN0 1 m’

r.PAVFI

n*?“l

.

I

CC6iNNNlTy DEVELOPMENT DEPARMENT t.llNlsTRY OF A4mcuLIuRE

. LWREO REPUBLIC OF CAMERa

HElMETAS

SWtS6 ASS4YJATION FOR TEcHNlw ASSISTANCE ( 5ATA 1

MANUAL FOR RURAL MITER SLWLY

PUBLIC FOUNTAIN

IN MASONRY CONSTRUCTION

30 90 130 LEAN

90 CONCRE

1 . 7 Y ‘I

SECTION A A

370

, 30 L 310

1

L 30

1

I ^I

PAVED FLOOR

110

I.[10 , -91

7

-

t

PLAN

:TE

KEY:

EEZZZl CEMENT BLOCKS OR

STONE MASONRY

EZZil CAST CONCRETE OR

STONE MASONRY

lSZZZ?Y REINFORCED CONCRETE

ISOMETRIC VIEW OF MANHOLE

SECTION B - B

BALL VALVE

-

VIEW C-C

COMMUNITY DEVELOPMENT DEPARTMENT MINISTRY OF AGRICULTURE

UNITED REPUBLIC OF CAMEROON

HELVETAS

SWISS ASSOCIATION FOR TECHNICAL ASSISTANCE ( SATA)

“. ,_ r

_I_ >

_” ‘,

MANUAL FOR RURAL WATER SUPPLY

DRAWN: BH

,’ DATE : MAY 1980

(a) D ACCORDING TO THE MEASJJREMENTS

OF THE BALL VALVE

OVERFLOW AND CLEANING PIPE -

SECTION A -A

Cl = CLIMBING IRONS

J I/ I

DRAIN PIPE

I I

GROUND PLAN

,,

INTERRUPTION CHAMBER

-./

), WITH BALL VALVE NORM PLAN

.( ‘,:

..’

.‘b~..‘;‘,,.. (.f,.‘ ,,’ No. 5

: ,’ ._ I)

<‘,. I~

i I. ’ 2; _,;, ;,

.-

,,‘(

,‘.

?,...’

.,:

-, i‘

‘,

STORAGE VOLUME :

ACCORRING TO THE YIELD OF THE SPRING

DURING DRY SEASON AND TO THE DAILY

CONSUMPTION

RETAINING WALLS ACtOR

TO THE TERRAIN

KEY :

STONE MASONRY

CAST CONCRETE

-

SECTION B -B

REINFORCED CONCRETE

ISOMETRIC VIEW

SECTION A -A

StLIIUN C-C

SECTION D- D

L. I

-4uNlTY DEVELOPMENT DEPARTMENT

:n Dcc4 im tm -- -. . .-m--m. MINISTRY OF AGRICULTURE 1

: I

YYI.1,.

UNITL, l-h1 QJPLIL ur LAMkKUUN

.,

HELVETAS

_,.,I _^ -mm--. ---

SToRAGE :IEANING PIPE

,?%

>WI>S ASSLKIATION FOR TECHNICAL ASSISTANCE ( SATA)

&:;Q.:, ,;. I

‘)_ i

J,.

:,,.

MANUAL

FOR

RURAL WATER SUPPLY

ORAW N :

c ., ‘, DATE : MAY 1::

,r ,,. _, ‘ ’

*,>.. ”

& . .;,)

C’.~ s,.

WATER POINT

-.I:‘.’ ’ / IN MASONRY CONSTRUCTION

: ,. NORM PLAN

,I_i I.

DRAIN PIPE OR

DRAIN CHANNEL

GROUND PLAN

AERATION WITH

f+ PROTECTIVE COVER

I

T’T-

BALL VALVE

TAP

7

> - GATE VALVE OVERFLOW ~

i

+r -

.-__ -

-.

b AERATION DISTRIBUTION

-w -

- -

SUPPLY FROM

CATCHMENT (FILTER )

-

I

DISTRIBUTION

STRAINER

[ KUGLER 619111

- OVERFLOW PIECE

[ KUGLER 61642 1

AND CLEANING PIPE

COMMUNITY DEVELOPMENT DEPARTMENT MINISTRY OF AGRICULTURE

UNITED REPUBLIC OF CAMEROON

: .~ HELVETAS

SW&S ASSOCIATION FOR TECHNICAL ASSISTANCE (SATA 1

DRAWN BY BTC

DATE : MAY 1900

PLUMBING SCHEME

SINGLE STORAGE TANK

AERATION WITH

PROTECTIVE COVER

7

BALL VALVE

-

I

OVERFLOW GATE VALVE

I

STRAINER

[KUGLER 61911 I

- OVERFLOW PIECE

IKUGLER 616421

COMl’dJNlTY DEVELOPMENT DEPARTMENT

CC%ll’dJNlTY DEVELOPMENT DEPARTMENT MINISTRY OF AGRICULTURE

MINISTRY OF AGRICULTURE

: UNITED REf’UBUC OF CAMEROON UNITED REf’UBUC OF CAMEROON

HELVETAS HELVETAS

,;

!, SWISS ASSOCIATION FOR TECtiNlCAL ASSISTANCE (SATA 1

SWISS ASSOCIATION FOR TECtiNlCAL ASSISTANCE (SATA 1

;; ,:: ;; ,::

,; I ,; I

MANUAL FOR RURAL WATER SUPPLY

DRAWN BY BTC DRAWN BY BTC

.,_ .,_ DATE DATE : MAY 1960

: MAY 1960

I\: I\:

:: ::

2.. 2..

I. I. ’ PLUMBING SCHEME OF

’ PLUMBING SCHEME OF

$ $

l:; l:;

DOUBLE STORAGE TANK

SCHEME PLAN SCHEME PLAN

I I

; .i ; .i

,._, ,._,

i..,: i..,: No. 0 No. 0

b’j. : b’j. :

&IL: &IL:

,p:> 2:, -,;,; ,p:> 2:, -,;,;

;f,;; ; ;f,;; ;

AERATION WITH

PROTECTIVE COVER

-. BALL VALVE

r AERATION DISTRIBUTION

TAP

c GATE VALVE OVERFLOW

i

I t. .

SUPPLY FROM

CATCHMENT(FILTER1

I

STRAINER

[KUGLER 61911 I-- @ DISTRIBUTION

TO VILLAGE -;

I-

GATE VALVES

L

PLUMBING SCHEME

DOUBLE STORAGE TANK

COMMUNITY DEVELOPMENT DEPARTMENT

TECHNICAL SERVICE BAMENDA I

MANKAHA - BAFUT

WATER

DRAWN: l

DATE : 10:03:?5

HODiFYD:O.NC

HYDRAULIC

MUM NEKURU

SEAT PUBLICATIONS

Publ.

No.

1.

Jean-Max Baumer: Schweizerische Kontaktstelle fur Angepasste

Technologie (SEAT), St. Gallen 1977, 39 Seiten, gratis

2. Jean-Max Baumer: Angepasste Technologien fiir Entwicklungslgnder,

Literaturstudie, St. Gallen 1977, 132 Seiten (out of print)

3. Jean-Max Baumer: Angepasste Technologien fiir Entwicklungsldnder,

Bibliographie, St. Gallen 1977, 307 Seiten (out of print)

4. Jiirg Nipkow: Angepasste Technologien fur EntwicklungslZnder,

Sonnenenergie-Gerate fur Haushalte, St. Gallen 1977,

62 Seiten, Fr. 8.50

5. Sabine Huber: Probleme des Technologie-Transfers von Industrie-

13ndern in EntwicklungslBnder, St. Gallen 1978,

43 Seiten (out of print)

6. Gerhard

Schwarz:

Hemmnisse und Hindernisse bei der Verwirklichung

des Konzepts der Angepassten Technologie in Entwicklungs-

Cindern, St. Gallen 1978, 53 Seiten, Fr. 14.--

7. Otto Langenegger: Einsatz von Bohrmaschinen fiir die Wasserbeschaffung

in Aethiopien, St. Gallen 1979, 43 Seiten, Fr. 14.--

8. Helvetas: Manual for Rural Water Supply, St. Gall 1980, 175 pages,

with many detailed constructional scale-drawings, SFr. 34.--

(US$ 20.--j

Manual For Rural Water Supply

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