Manual For Rural Water Supply

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A project of Voluntesrs in Asia

by: Swies Ca?ter

for Appropriate

Published by:
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WITHMANYDETAILED
CONSTRUCTIONAL
SCALE
-DRAWINGS

Publication No. 8
St.Gall 1980

Varnbgelstr 14
CH-9000 St .Gallen
Tel. 071 I 23 34 81
MAT
wsiwisohe Konllllttslelle
tPr AngepamteT@hnik
ull J~rtltut fgr Lsteinamsrikafaraahung wd Entwldrlunguuwnmen~wJM&zr HrMWwle WWlen

SKAT
SWISSCenter for
Appropriate Technology
at the lnrtltute Iw Lstln-American
Research and for Development
Cooperstlon, St.Gall University

SKAT
Centre Suisse pour la
Technologle ApproprMe
a I’lnstltut Latino-Ambricain
et de Coop4ration au DBveloppement, 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
WITHMANYDETAILED
CONSTRUCTIONAL
SCALE
.-DRAWINGS

Publication No. 8
St.Gail 1980

Edited and
compiled by:

Helvetas, Swiss Association
for Technical
Assistance,
Zurich, Switzerland
and Yaounde,
Cameroon

Cover photo:

HELVETAS

Published

SKAT, Swiss Center for Appropriate
Technology
at the Institute
for Latin-American
Research
and for Development Cooperation,
St. Gall
University

by:

Comments,
enquiries:

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.

Price:

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
step towards
and transmitted
by polluted
water, but is very often the first
other development scopes like health, nutrition,
sanitary programmes, etc.
and socio-economical
When a water supply is being planned, all technical
As one of the consequences simple
aspects have to be considered carefully.
techniques,
simple designs, and a simple system are used. In this context
greatest attention
has to be paid to the fundamental problem of maintenance,
of a project.
that is even before starting
with the construction
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
engineers and field staff who arc
to provide Community Development officials,
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
improvement of the water conditions
in developing countries.

Our sincere thanks go to all
of this Manual.

persons who have been involved

to a general
in the preparation

May 1980

HELVETAS
Swiss Associa'tion
for Technical Assistance
St. Moritzstrasse
15

HELVETAS
Swiss Association
for Technical Assistance
P.O. Box 279

8042

Yaounde / U.R. Cameroon

Zurich

/ Switzerland

(SATA)

Foreword

by the

It is very fitting
an organization
construction
in
and compile and
a comprehensive

Publisher

at the beginning of the UN decade dedicated to water that
that has got a vast experience in rural water supply
developing countries
should decide to make a special effort
edit material of field engineers to make tv,e publication
of
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
Despite its being based on experience in one specific
Cameroon (West Africa).
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.
safety standards for drinking
water,
Manyfold aspects such as hydrology,
and maintenance, spring catchments,
design of water schemes, construction
systems and water lifting
are
barrage and river intake systems, distribution
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
stable quality
of drinking
water
to achieve systems of trouble free operation,
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
alternative
technologies
such as alternative
the use of hydraulic
rams. Specific
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
..-m__ - SUMMARY

HYDROLOGY
l-l
l-2
1-3
l-4

CHARACTERISTICSOF WATER

2-l
2-2
2-3
2-4

17
19
22
2G

Water sources
Standards for drinking
water
Aggressivity
of water towards
Prevention of corrosion

building

material

INVESTIGATIONS AND BASIC DATA FOR RURAL WATERSUPPLIES

3-l
3-2
3-3
3-4
3-5

33
34
35
35
40

General fieldwork
Specific consumption
Location cf water source
Measuring of water quantities
Analysis of water

DESIGN AND CONSTRUCTIONOF RURAL WATERSUPPLIES

General lay-out
Wells
Spring catchment
Water point
Barrage and river intake
Water treatment
Storage
Distribution
system
Water lifting

49
55
65
78
80
83
99
103
139

ADMINISTRATION OF PROJECTS

151

5-l
5-2
5-3

153
156
156

4-l
4-2
4-3
4-4
4-5
4-6
4-7
4-S
4-9
5.

5
6
13
14

Definition
and hydrologic
cycle
Climatic pattern and rainfall
Run-off and infiltration
Drainage in Cameroon

Technical report
Execution of project
Completed project

MAINTENANCEOF RURAL WATERSUPPLIES

159

6-l
6-2

161
161

Maintenance
Maintenance

general
instructions

SELECTEDBIBLIOGRAPHY

167

INDEX OF KEY WORDS

169

Appendix:

PLANS AND SCHEMEPLANS
(Constructional
Scale Drawings)

NORM

Chapter

HYDROLOGY

Table of contents

page

l-l

DEFINITION AND HYDROLOGICCYCLE

1-2

CLIMATIC PATTERNAND RAINFALL

1 - 2.1

Quantity

1 - 2.2

Variation

1 - 2.3

Tables of monthly

1 - 2.4

Intensity

1-3

RUN-OFF AND INFILTRATION

1-4

DRAINAGE IN CAMEROON

of rainfall
of rainfall

rainfall

of rainfall

13
14

DEFINITION AND HYDPOLOGICCYCLE

l-l

Hydrology is the science of distribution
and behaviour of water in nature.
Cycle
The
cycle
of water or Hydrologic
Hydrology is a part of climatology.
is without beginning or end and consists of the following:
- Precipitation:
of the earth

All water from the atmosphere deposited
as either rain, snow, hail or dew.

on the surface

The water which is derived directly
from precipitation
- Surface run off:
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.
Combined loss of water
- Evaporation,
transpiration:
surfaces by evaporation
and plant transpiratjon.

from land and water-

- 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
movement 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 watertable.

Fig.

Hydrologic

Cycle

CLIMATICPATTERWAND RAINFALL

l-2

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
inadequate records in terms of duration
and number of stations.
Nevertheless, 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 NorthWest 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
same annual rainfal1
of the distribution

l-2.2

can be mapped with isohyets,
are linked and the resulting
of the rainfall
in a region.

i.e. all points with the
lines give us an idea
(see Fig. 2 and 3!

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

Fig.

_Isohyetes

West-Coast

(1967)

Fig.

Distribution

1
2
3
4
I

OVER 375 cm
200 - 375 cm
SO - 200 cm
100 -1SOcm
700--tOOem

BELOW

of annual

rainfall

6
!s

FouRtAU
70 am

cm
.
.

.
.

..*...
.

..a..
.

.
.

‘*

‘**:

.
---I

.
’

. *
.
. .

FiG.('$

Bnd 5

.,.

rainfall

. . ..i

-3

,.,

,ring (continuous flow).

Fig.

cracks

the flow volume of the spring.

will

influence

the flow volume of

SPRINGS
SPRING -1

ARTESIAN

SPRINGS

NWL a ~I&CRW#W~~R
PCRC~ATCINTO
LWL

2-1.3

= GAOlJM WaTLR fLows INTO TM
RIVER (INVISIU
SPRINGS)

STREAMS

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

STANDARDSFOR 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

HACTERIOLOGICALSTANDARDS

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 recommended for treated and untreated drinking-water
for present use
throughout the world.
Coliform density
100 ml of water,

is estimated in terms of the "most probable
called "MPN" Index.

To get the coliform bacterial
count (MPN Index)
Laboratory can be used (see chapter 3-5.1).

of the water,

number" in
the Millipore

sted Water (by chemicals1
ia shall not be
shall be less than 1.
detected or the MPN index of coliform micro-organisms
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
samples or in mDre than
exceed 4 per 100 ml either in any two consecutive
10 % of the samples examined.
Cheamical treatment of water (e.g. chlorination)
CD/SATA-Nelvetas projects
in Cameroon , mainly
a continuous rupply of the products.

b) Untreated
Very often
dieinfected
etand

water

(incl.

slow sand filter

has not been applied
because of uncertainty

without

in
of

chlorination)

communal drinking-water
is not chlorinated
or otherwise
before being distributed.
In such water schemes the following

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
to the water supply should be considered.

_ when the micro-filter
technique is
arithmetic
mean of the numbers of
shall be less than 10 per 100 ml,
two consecutive samples or in nmre
This standard
2-2.1.3

is applicable

for

all

of treatment

used in examination of water, the
coliform group bacteria determined
and shall not exceed 20 per 100 ml in
than lo& of the samples examined.

the CD-SATA-Helvetas

water

supplies.

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 drinkingwater 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
Arsenic

0.05
0.05

Bel.enam

0 ,Ol

Chromium
Cyanide
Cadmium
6axium

0.05
0.2
0.01
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
cannot
different
parts of the world , rigid standards of chemical quality
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
in specific
instances.

are indicative

IIHX.

500 mg/l

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

1500 mg/l
1.0
150
0.5
1.5
15
200
400
600
1000
0.002
0.5
1.0

0.3 mg/l
"
50
0.1
W
1.0
W
5.0
lo
II
75
II
200
II
200
,s
500
0.001 lU
0.2
))
0.5
@a
7.0 - 8.5

pH Range *

*This item can be analysed by field tests, the
out only in a laboratory
(see chapter 3-5.2)

2-2.2 -S

all0wabl.e
concentration

max. acceptable
concentration

Substance
Total

only and can be disregarded

mg/l
I,
In
W
"
II
w
I,
I,
w
w
((

less than 6.5 or
greater than 9.2

others

can be found

FOR DRIWKIWG-WATERIN CAMEROON

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
"Conseil HupBrieur
d'hygiine
publique"
and the decrees of 28th February,
1962 and 7th September, 1967.
There correspond

mite or less with

international

standards.

?
i
;

2-3

AGGRBSSIVITY OF WATERON 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
or not depends much on the
*these two values prove aggressive
carbonate hardness ot the water. That is why these three magnitudes
are described more in detail below,
PH - VALUE

2-3.2

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.

PH-value for neutral
on the calcium salt

watk- depending
content

8,8
w

8,4
8,2
8,O
%7,8
T76
’ 7:4
E7,2
7,O
d-’

’

DG’

’ 1

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
0

2-3.3

CARBONDI@JXDfI

Summary :

Only part of the carbon dioxide in water (the excess CO21 is aggressive
The theory on this page shows the contowards cement and iron products.
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
\
Fixed carbon dioxide
Freee carbon dioxide
/
------.
Fully fixed CO2
Half
Associated CO2
CaC03 in
carbonates)
not aggressive

(harmless to
concrete!

total excess
(prevents formation
of anti rust layer)

fixed

CO2

Ca (HC03) 2
in hydrogen
carbonates 1
not aggressive
(e.g.

Partial
excess
(lime aggressive,
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
Therefore
hardness:

fixed carbon dioxide is combined with calcium or magnesium.
its amount can be calculated
according to the carbonate
ODG 7,f35 = mg/l of fixed carbon dioxide.
l

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.

The associated

0
d

2il

carbon

dioxide

EiO 100 W 140 160
fixed CO2 mgll
2I - 4I . 6I . 8I _ 10
I . I2‘ 11
a - I6y120
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 carbonate 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.

~ggressivfty
towards cement products
(concrete,
mortar,
AC-pipes) depmding on the DG and the free CO2

Fig.

2 4 6 8 10 12 14 16 18 '20 22
carbonate hardness ” DG

Aggressivity
towards iron products
on the DG and the free CO2

(steel

4 6 8 Dl2l416182022
Carbonate hardness @DG

pipes)

depending

The hardness of water is dictated
by its content of calcium and magnesium
salts, Water containing
much calcium ano magnesium is termed hard, that
soft, This is expressed numerically
by the degree of
containing
little,
hardness. Unfortunately
there is no international
unit established
so far.
Degree of hardness

- conversion

1 grain CaCOJ/gallon
10 mg CaO / liter
10 mg CaC03/0,7 liter
10 mg CaC03/ liter
10 DG
lo DG
Degree of hardness

modulus:
=
=
=
=
=
=

17,l mg CaC03/1 = 0,96ODG
1 German degree of hardness (ODG)
1 English degree of hardness
1 French degree of hardness
1,25 English degree of hardness
1,78 French degree of hardness

This water is termed as

OlG
o48 12 18 over

4
8
12
18
30
30

Three different

very soft
soft
medium hard
considerably
hard
very hard
kinds of hardness

hard

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.

24.2
Cement, mortar,
vhich dissolves

concrete, aslmstas cemant pipe
in contact with sggre

conbin

calcim

carbn&te

2-4.2.1
- Acid v&tar @I v&u@ kmlow ths neutral
am h88rmfui to concrete,
It hamu*
blow
thf3 neutral
than 1 to 2 point

, Pig, 11.) must kr regrrdd
rmful if the pH value is more

1
line.

- AS it can be seen from Fig. 13, soft water (with IOU carbnate
hardness)
This
becumes always very aggressive if it contains free carbon dioxide.
concrete
and
mortar
and
aclgresoive CO2 dissolves
the calcium salts of the
ng water with such
ic dastroys gradually
theBe cement product
very rapidly.
cr Alkmlim

watw

11,
the
mg/l in flowing wif
%xtrPnt also the corresponding
Qnt

~11
-

Ham%ul

line) can ill~ilo CBUP~ d
above 300 mq/l in satanding
magnesium 5ulphates
and, tc3 zi
, dsetroy concrete,
chloride

to concrete is als~s wetlsr containing
alfum salt5 (@.g. wa

- cuncrQt;8 is
(

(Fig.

&x’oducto

idly

ttackQd by vat r containing
in ceartal

arsPrs1.

hydrogen

sulphide

and larger

~~Iium hydrogen carbonate

nt than porous concrete.
t pus”Lbla water-

t E*ternd
such as
spetrion), plastic

occuxfng

wkth &SW

It the o%yfpn content
bilky

W&ld&ty

im OXUW~IVI,

of wtex),

iron

not in genuinely

diouolved

form

attacked.

irr likmhe

- Iron im elbmymattmkad and bimsohd ky water
uhich

preventa

ena Pig.

14)

containing
~ree8tv.e
of a protective
layer against

thm forution
l

- I& &B-value @hould altray
be equal
unprotected
iron piparr
-Cl,5 point*

to or juot below the equilibrium
for
for gelvanieed
steel pipes (see Fig.

- Unp+akcted

by hydrogen

iron

pipem ere attacked

- Wnt8r with

a high

rtmmgly.

The Limit

chloride

eontmt

for unprotected

mulphlde

(e.g.

in B-soilr

brackish
vater)
attacks iron
pipes icr L5Omg/Liter in aoft

(e.g.
iron

pipe6

water,
- sp+cibl
- Steel

bar to bm given

to the e&mnal

attack.

pipes ue mre twuceptib~e
to chemlcrrl attacks
&ton pipee ue more reeirrtant
than steel pipes
oxygen eontent and aggremive
properties.

bet
high

24.3.2

rttention

of corro8ion

of the recrreroive

crcbn

Ptevuntbn

- llrdwtion
- &on

piper

c?ailatd

m&l@,

have to be coated

*@ynapLmt~~in
lou end clay

GIW

dioridsr

~4th little

re chapter

cast iron pipes.
soft water of

2-4.2.2.

of coal4.ar
pitch
(eoamm3eelvity
(e.g. in acid peaty
calc$un and in salty ground water etc.1 .

by relted
of

than

against

ewtawnal

bit-n

11)

2-4.4

PMSTIC PIPES

Plastic pipes are either
(see chapter 4-8.2.31.

of PVC (polyvinyl

Since 1959 the fabrication
of plastic
to the claims of water engineering.

chloride)

or of PE (polyethylene)

pipes has been adapted more and more

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
in particular
with aggressive water and soil. Nevertheless
water supplies,
much attention
has to be paid to an adequate fabrication.
Some plastic
notably
poor
polyethylene
pipes, serve as nutrient
of bacteria.
materials,

2-4.5

EXAMPLESOF PRACTICAL,APPLICATION

To show the practical
application
samples will be analysed:
Sample

of chapter

2-4 three different

water

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:

This "soft"
aggressive"

PH = ,7,4
Hardness = 7 grains CaC03/gallon
(=7,7ODG)
Content of carbon dioxide
(CO21 = 42 mg/l

water
(Fig.

(chapter 2-3.4) is little
acid (Fig. 11) and "very
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
(=10,5O DG)
Hardness = 11 grains CaCO3/gallon
Content of carbon dioxide (CO2) = 18 mg/l

This “medium hard”
"little
aggressive"

water (chapter 2-3.4) is little
acid (Fig.
(Fig. 13 and 14) towards cement and steel

Conclusions:
In this water project

all

common building.znd

applied.

piping

materials

111 and
products.
can be

Chapter

INVESTIGATIONS AND BASIC DATA FOR RURAL WATER SUPPLIES

page

Table of contents
3-1

GENERAL FIELD WORK

3-2

SPECIFIC CONSUMPTION

3-3

LOCATION OF WATER SOURCE

3 - 3.1

Source situated

3 - 3.2

Spring

3 - 3.3

Source situated

3-4

MEASURING OF WATERQUANTITIES

3 - 4.1.

General

3 - 4.2

Estimating

3 - 4.3

Measuring

3 - 4.4

Flow measurements with a weir
3-4.4.1
Thompson weir
3-4.4.2
Rectangular weir

37
37
38

3-5

ANALYSIS OF WATER

3 - 5.1

Bacteriological.

3 - 5.2

Chemical analysis

above consumer

water

below consumer

water quantities
water quantities

of a stream
with

a bucket

and a watch

test

of water

field

GENERALFIELD WORK

3-l

The following
list intends to give a summary of the field
planning and construction
of a rural water supply:

work during

- Application
for assistance
is sent by the community concerned
Community Development Department (CD) or to the local council.

to the

- 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
- Preliminary
the results

(springs,

river,

etc.)
followed

survey with pocket altimeter,
with the community.

- If the project

is feasible

collection

a) Situation:
Geographical
function of the village

by discussion

of more information

and data on:

and administrative
situation,
in the region, etc.

place

and

b) Population:
Number of inhabitants,
ethnological
composition,
development of the population
during the past years,
denominations,

etc.

Present infrastructure
and development plans of roads,
c) Infrastructure:
schools, markets, health centres,
cooperatives,
missions, other
development projects,
etc.
d) Economic aspects: Produce and income,
potential,
farms, markets, industries,
development projects,
etc.
- Contacts

to other

- Measuring

of the water quantity

- Biological
- Detailed

Government Services,

and chemical

cooperatives,
coordination

agricultural
with other

Local Administration

of source

water tests

(see chapter

3-5)

survey

- Occurence and quality
stones and wood.
- Technical

report,

- Organization
of a project

of local

estimate

building

(see chapter

materials:

Sand, gravel,

5-l)

of community by Community Development Department
committee if not already done)

(organization

- Financing of project:
application
for government grants and foreign aid,
commitment to an amount for village
contribution
- Organization
of community work by project
committee
Development Department according to the instructions
- Implementation
- Organization

of project
of maintenance

(see chapter

33
,:,,. '
, ', :

and Community
of the technical

staff

3-2

SPECIFIC CONSUMPTION
average daily
at present
Stage O*
Village in remote areas
per head
Village with school, maternity
and max.lO% private
connections
per head
Urban areas with max 20%
private connections
per head
Residential
areas
(private connections)
per head
Primary school
per pupil
College
per student
Maternity
per bed
Hospital without Surgery
per bed
Hospital with Surgery
per bed

water consumption
in litres
in future
Stage I*
Stage II*

5r)'

100

1c:o

120

100
10
100
100
100
200

200
10
120
100
150
300

250
10
120
130
150
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!
Market
The smaller the community, the greater,
in general, is the variation.
days and local celebrations
can have a big influence
on daily water consumptic
The following
values have been experienced:
Ratio
Maximum day:
Maximum hour:

average day
average hour

Normal rate
(from 1.2 to 2.0)
(from 2.0 to 3.0)

:
:

1
1

Average
1.5 : 1
2.5 : 1

Measurements in the Ngondzen water supply have shown the same results.
* see chapter

Fig.

15
Q%

Daily

4-1.2.2

consumption

in a rural

water supply

3-3

LOCATION OF WATERSOURCE

3-3.1

SOURCESX_?~Ui'i'l'ED
ABOVE CONSUMER

all possible water sources have to be investlqatf~~i
wtrtttlrbr
With
tl,
they can supply wst?r by gravia
to the consumer. It is *.ast prf~fcrdt~lf~
get water by gravity
in order to avoid the installation
of an enqinr: (Imp,
water to the consumer). In this way the maintcnancr: will
ram, etc. to lift
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

SOURCESITUATED BELOWCONSUMER

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

MEASURINGOF WATERQUANTITIES

3-4.1

GENERAL

The most important
water available.
Before we start
be considered.

figure

detailing

for any kind of water-works
a project

is the quantity

we need to know how much water

of
has to

- 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).

,.
$j&
,6 ,:

”

34.2

ESTImTI?$

The quantity

Q
A
v
s

=
=
=
=

WATERQUANTITIES Of? A STREAM

of water

flowing

steadily

In a stream is

quantity of water (m3/sec!)
cross-sectional
area of flow
(m2)
velocity
of water (m/set)
surface: for plastered
surfaces
for rough rocky surfaces
average

To estimate

the flow of a stream carry

= 0,9
= 0,s
= 0,6 - 0,8

out the following

procedure:

- determinesthe
cross-sectional
area of the water flowing
(average
depth of water x width of stream = A)
velocity
of water:
take the distance that a piece of wood or a leaf
second (Xm/sec), out of three measurements.

in a stream

- measure

- calculate

3-4.3

the quantity

of water as a result

travels

during

of 1 and 2

Q=Axv

one

MEASURINGWATERQUANTITIES WITH A BUCKETAND 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,
earthdam so that all the water passes through

are fitted
the pipes.

into

a temporary

- 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
records.
- Calculate

the quantity

in l/min.

times and enter
or l/set.

the results

into

the

3-4.4

FLQWMEASUREMENTS
WITH A WEIR

3-4.4.1

Thompson weir

This method is suitable
The following
Fig.

for quantities

arrangements

up to about

l/see.

have to be made:

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
- normally a 900 weir is used x
Y
- important:
The gauging rod must
the weir. The zero point of the
crest of the weir.

be in a distance of at least
rod must be on the same level

Fig.

0.4

0.6

1.0

1.2

1.4

I.6

2.0

U IN

1 m/set

gauging rod =
= 2

2.2
U5LI;
L/SEC

2.4

Discharge

over

2.6

3.2

2.0

3.0

h from
as the

Thomson weir

3.6

3.0

4.0

4.6

Fig.

Discharge
tl- =

oyer

Thompson weir

11 - 20 cm

xb
r

h
ON
1
2

3
:
t6

u I2

I IY

i
10
11

2 &-=90’

13
14
15

h=19om

:;
18
1Y
20
22

’

3-4.4.2

4’6

Rectangular

12 14 16
0 in L/SEC.

Fig.

for quantities

arrangements

- maximum velocity

0.008
047
Alo
266
465
733
l.UlO
1.5%

0.014
081
224
461
805
1.270
1.867
2.606
3.50
4.55
5.78
7.18
8.W
lo.%
12.54
14.75
17.16
19.79

2.020
2.63

3.34
4.15
5.07
6.10
7.25
0.51
9.91
11.43
13.cq
14.87
18.88
23.47
20.66
34.5
41.0

22.67
25.76

32.7
40.6
49.6
59.7
71.0

above 10 l/set.

have to be made:
SalION

PROFILE

- minimum H =

2
900

weir

'This method is applicable
The following

Pb
28
30

1.155
600

4 h
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 crest

the minimum width

for a weir

should be 50 cm, better

of the weir must have a sharp edge.
38

1.00 m

Fig.

Discharge
t

15
14

over
1

rectangular
I

weir
I

h=lZcm
b=
BOcm
EXAMPLE
FROM TABLE Q = 748 llsec
x 08m
= 6OOllsec
FROM GFfAPH 0 = 750 llsec
x OBm = 600 llsec

la-;-

I
I
I
I

1
lo

I / sec.

h in
a

'3 i~ll/s
&r3-L&

bin
AAL
26

$
$

::;
6.7
5.1

3
4
5
6
7
i

9.4
14.4
20.1
26.5
33.3
48.6
40.7

10
ll
12

56.9
65.7
74.8

13
14

2::
104.6

15
16
ii

u5.2
137.5
126.2

19
20
22
24

149.2

225

161.0
l86
2l2

V in l/o
for B -l.oq
239
267

:
::

;:
357

:2
38
40
42
44
45
46
48

:;
60
65
70
75
80
85

tit

50.60

422
455
490
525
543
561
599

z
1054
2169
la8
1411
%

loo

‘;-.“:

3-5

ANALYSIS OF WATER

3-5.1

BACTERIQLOGJCALFIELD 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
with CD-SATA-Helvetas:

kit

and monitors

from a bacteriological

Remove the plastic
aside.

Carefully
insert the syringe valve connection
side) of the monitor. Avoid excesz,ive force.

Remove a sterile
sampling tube from its
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.
quick strokes to pull the monitor as dry as possible.

Remove and discard

Crack off the ti.p
do not remove the
the plastic
tube,
bottom tip of the

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

the sampling

tube,

monitor

which is availab

10.

plugs

water analysis

into

and set them

the bottom

sleeve and insert

("spoked"

the nylon

tip

Use short,

but do not remove the monitor.

of an ampoule (covered by a short plastic
tube), but
tip or the tube. Place the forefinger
over the end of
as when using a pipette,
and break off and discard the
ampoule.

Replace the plastic
plugs, invert the monitor, and incubate at 35OC
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.
In some cases it may be difficult
fecal origin
(from intestines
of
from other environmental
sources.
at 44OC for 24 hours. The colonies
Conditions
are certainly
coliform

to differentiate
between coliform of
warm-blooded animals) and coliforms
In this case a sample may be incubated
which are growing under these
of fecal origin,

11.

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)

12.

For more detailed

instructions

see "Millipore-Manual".

3-5.2

CHEMICAL ANALYSIS OF WATER

general
laboratory

chemical analysis of water has to be carried
(e.g. of a hospital
or a high school).

out by a well

equipped

general analysis a sample of at least 2 litres
is required.
It should
collected
in a chemically clean bottle made of good quality
(neutral)
glass, practically
colourless
and fitted
with a ground-glass
stopper.
For
be

In the collection
completely filled

of samples from mineralized
sources,
and the stopper securely fastened.

the bottle

should be

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
CD/SATA-Helvetas water supplies.

partial

If a general chemical analysis
is not possible,
analyse the water by a field test. Additionally
out from the local population
whether the water
Chemical field

test

- Content

of carbon dioxide

- Content

of dissolved

- PH-value
The test

procedure

of different

the design engineer has to
the engineer has to find
is potable or not.

(Hach)

With the portable water analysis
available
with CD-SATA-Helvetas,
measured:

- Hardness in grain

analysis

kit (model CA-24WP) of Hach, which is
the following
chemical values can be
(CO2) in mg/l

(see 2-3.3)

oxygen in mg/l

CaCO3/gallon

(see 2-3.4)

(see 2-3.2)
is described

in Fig.

22.

ChemLc8.l water
Dreignation
of tha
estsr aelmas:

OIAW~ 35 223

c-’

Helvetas
sehweiter
Aufbauwerk
EntwickluIlgsl~er

wlalslmob--m
wngNnn*tYOvrnJUOr*w
-ucaewemmNr-

(in %G]:
hnrdness

Urbanate

fiir

vom 1, Derember 1975; Ref. W/ii

m:
wmw-.

Result
Sanplss:

five
the

ootties
rith
very
Taxxings

Chmical

malysis

The analyzed
extraordinary

samples
litt+e

samples
(but
(lime-aggressive

eeeciafiy

&cause

catian
the

tested

waters

Dn the

orher

1 litre
pure
rater,
each and an admixture

are
salts

and
little
and

"Kai"

aCditiOt%?+lly
3i calcium

Settles
ccrznnate.

with

cl.17

0.17

1.45

0.1

I.7

0.5

005

0.15

0.2

0.B

0.1

G.75

herdnesr
of

as/l):

(in

Sulfate8

60,

Chlorides

acia
to
also
very
ana *‘:ieh”j

neutral
iittle

heve

and extremely
soft.
They contain
orgnic
pollution.
All
the
3 high
anility
to dissclve
iiira

dioxide).

small
hardness
are aggressive
hand.
tnare is

soft
rater)
ails
cement
as well
qejection
to the use

(very
?cwards
no

tha acid
as towards
cf plastic

character,
steel.
material.

Co,

dioxide

Natrium
NanCOg
Uagnesium

examinatmn

the

7.0

Total

Calculated

five

6.0

1.7

7.7

(Hey-f
tCUdl4 consixrmtifm
in mail

(translation!

6.b

0.1

csrtmn

Vemuchsefgebnir - Msultat - Rlsultato

5.9

1.0s

Alkalinity
ml/l:
Yethyromnge

nach Angaben

6.6

0.17

Lime-eggressive

Chemische Analyse

sehn

0.17

colltent
Ksmmm

Gsh

carbo~te
hsrdllsss

Non

FXtnf Doppelproben ksser
betr. &A.T.A.
Wasserversorguag.

Brief

3etrifff:

PH -U&la

Htwdness

Zurich

G==%l

amlysis

Dueoendorf.

1.6

37.4

0.6

a.6
0.9

8.e

1.6

0.9

mgjl:

olWnete
7
ISg

the

gth

December

l2
0

195

24
2.4

5
0

13
3.5

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 POWdsr 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 Omxgen 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
us 3 mq/l or less. It (s Jdv~wble
IWQW wmple to nbtam a more
rmult.
Thcs may be dclne by
duectlv
m the DO ra~lpls
f0llwn:

low. such
to test a
%anrltwo
tltratmp
bottle as

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 8squaI to
0 2 rndl dissolved oxygen m thr sam
pte. &e Note E.

MODEL

CA 24WR

Hdness

Test

1. Add 3 drops of Mutter Solution.
~WSS1 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

NOTES Dwx~lvedOryga,
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 msertthe 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*.

It&

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
Intl~cJtor Solutmn
end zwwl to m,x.

Wide HJnge 1 pH
to me of the tubes

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
The

pH
praEencs

a! chlorww

mple ~111
cd”w J slqht

an Ihe vrJtrt

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

4-l
4

- 1,l

Syetxm

4-1.1.1
4-1.1.3
4-1.1.4
4-1.1.5
4-1.1.6
lMnp0ral
4-1.2.2
4

- 1.4

4-2

water

supply

lay-out in stagea
Servicxz life
tbsign in otago&3

4-1,Z.l

4 - 1.3

th?

Spring water by gravity
Stream water by gravity
Spring water bl?low the consumers
Supply of ground water
Stream below the consumers
Rain water storage

4-1.1.2

4 - 1.2

LAY-OUT

GENERAL

WWIpl@~

Materials

and construction

methods

WELLS

2.1

General

4 -

2.2

Types of wells

2.3

sire

2.4

Construction
methods
4-2.4.1
Native system

of well

4-2.4.2
4-2e4.3
4-2.4.4

Dug welis
Sunk welle
Sinking a tube well

SPRING CATCHNHNT

4-3
4

3.1

Quality

3.2

Location

- 3.3

a = 3.4

and quantity

of spring

water

of springs

Catchment area
Spring
4-3.4.2
4-3.4.3
4-3.4.4
4-3.4.5

4-3.4.6

catchment

(conetructlon)

The 'real'
catchment
Supply pipe to the inspection
chamber
inspection
chamber
Outlet building
Common mistakes on spring catchment

WATERPOTNT

cawrwl

Construction

of a water point
45

BARRAGE AND RIVER INTAKE

Determining

magnitudes

for the position

of the

barrage

4 - 5.2

Design of barrages

4 - 5.3

Design of intakes

4-6

WATER

4 - 6.1

General

4 - 6.2

Sedimentation
4-6.2.1
Definition
general
4-6.2.2
Design of sedimentation
4-6.2.3
Construction
details

TREATMENT

tanks

4 - 6.3

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

4 - 6.4

Other filter
types
4-6.4.1
Rapid gravity
filter
4-6.4.2
Pressure filter

4 - 6.5

Treatment

4-7

STORAGE

4 - 7.1

General

4 - 7.2

Capacity

4 - 7.3

Design of storage

4-8

DISTRIBUI'ION SYSTEM

103

4 - 8.1

Lay-out
4-8.1.1
4-8.1.2
4-8.1.3

103

4 - 8.2

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

4 - 8.3

Design

4-8.3.3
4-8.3.2
g-8.3.3
4-8.3.4

station:

Lay-out

of a storage

tank

101

tanks

of the distribution
system
Type of distribution
systems
Pressure zones
Disposition
of taps

of the distribution
system
Hydraulic
calculation
of piping
Prevention of air pockets
Prevention of vacuum
Air
release valves and anti vacuum valves

105

110

4 - 8.4

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

1.20

4 - 8.5

Distribution
buildings
4-8.5.1
Public standpipe
4-8.5.2
Public washplaces
4-8.5.3
Public shower house

135

4-9

WATERLIFTING

139

4 - 9.1

Types of pumps

139

4 - 9.2

Hand pumps
4-9.2.1
Deep well pump
4-9.2.2
Wing pump

140

4 - 9.3

Centrifugal
4-9.3.1
4-9.3.2
4-9.3.3
4-9.3.4

143

4 - 9.4

Other pumping system
4-9.4.1
Hydraulic ram
4-9.4.2
Hydro pump

pumps
Planning of centrifugal
pump installations
Pump drives
Pumping stations
Data needed by an enquirer

148

GENERALLAY-OUT

4-l

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

SYSTEMOF THE WATERSUPPLY

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
requires little
the simplest : It supplies water of best quality,
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
to drinking
and cooking
season the water consumption may be restricted
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

below the consumers
5
In case there is no way to supply water by gravity
is situated on the top of a hill)
preference will
which can supply water of good quality.

a) Water

situated

is collected

I
(e.g. if the village
be given to a spring

from the source by the consumer

In or'der to ensure good quality
of water and some storage
a water point (see chapter 4-4) is constructed.

facility

(see chapter

are different
possibilities
to natural driving energy (e.g.
turbine or wind etc.).

There

4-1.1.4

mly

ground

4-9)

to do this. Preference will be given
water power: hydraulic
ram, water

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

In case of
above, this
maintenance
should only
technically
4-l

.I.

Pain

below the consumers

failing
to get water supplied from a source as described
But this
system requires skilled
system may be applied.
and the running cost will be high. That's why this system
be applied in areas where the maintenance is assured
and financially.

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,
per person and
bathing etc.) should be calculated
with 10 - 15 liters
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
Such a system consists usually
(preferably
by small slow sand filters).
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

TEMPORALLAY-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.

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
water supply. These declarations
are experience-data
of solidly
elements under skilled
maintenance:
expected

Element
spring- and stream catchment
storage tank, treatment station
buildings
(in concrete or masonry)
installations
under ground pipes
pumps, engines
4-1.2.2

of a rural
constructed
1 ife

service

30 - 50 years
over
10 over
10 -

50
20
50
20

years
years
years
years

Design in stages
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.
A co-n
village
in
has to be taken into consideration.
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
are usually
designed for the following
stages:

in the rural

area

Element

Stage I

Stage 0

Stage II

Catchment
intake
inetallatione

X
x

X
X

PLping eystein
main

pLpee

d&rtribution

pipee

Starage tank, treatment
buildings
inetallatlons
pmpsr engines

station
x
x
X
El

with

extension

facility

4-1.3

EXAMPLES

Before the single elements can be designed, a clear lay-out of the whole
should
water supply has to be worked out. This base for the calculations
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:
Stage I:
Stage II:

2'000 persons at 30 l/day
4'000 persons at 60 l/day
8'000 persons at 80 l/day

= 60 m3/day
= 240 m3/day
= 640 m3/day

to,7 l/s)
(2,8 l/s)
(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
1 Spring catchment with inspection
designed for stage II.
2 Pipe line calculated
(q=7,4 l/s).

for

chamber

stage II

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
is required.
6 Distribution

pipe,

storage

calculated

for

tank
stage I.

7 Any likely
extension
would have to be
included into the calculations.

I
Example 2
Short description

of the water supply:

A spring situated above the village.
Actual population
800 persons.
Expected water consumption:
Stage 0:
Stage I:
Stage II:

800 persons at 25 l/day
1'600 persons at 50 l/day
3'200 persons at 70 l/day

=
=
=

20 m3/day
80 m3/day
224 m3/day

(O,2 l/s)
(0,9 l/s)
(2,6 l/s)

Water balance:
The
and
dry
the
Lay-out

yield of the spring is 50 m3/day at the end of the dry season
about 140 m3/day at the peak of the rainy season. During the
season in stage I the consumption has to be limited.
For stage II
yield of this spring is not sufficient.
of the water supply:
1 Spring catchment with
designed for stage I.

inspection

2 Transport pipe designed
(q=O,9 l/s).

chamber

for

stage I

3 Storage tank calculated
for
(capacity about 40 m3).

stage I

for the peak4 Supply pipe, calculated
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:
Stage I:
Stage II:
(* = reduced

1'400
2'800
5'600
due

persons at 25 l/day
persons at 40 l/day*
persons at 50 l/day*
to high running cost)

= 35 m3/day
= 112 m3/day
= 280 m3/day

l/s)
(1,3 l/s)

to,4

(3,2

l/s)

Water balance:
The stream yields during the dry season at least
the consumption of stage II can be covered.
Lay-out

15 l/s.

Therefore

of the water supply
..
1 Stream catchment with a short-timesedimentation.
dam and intake
for stage II
for stage I
sedimentation
TER
After stage I this is the proposed
for a pumping station.

site

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,
(q = 1,3 l/s).

calculated

for

stage I

4 Treatment station:
Sedimentation
and slow sand filters
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

6 Main supply pipe,
7 Distribution
4-1.4

pipe,

calculated
calculated

storage
for

designed

tank is required.

stage II.

for

stage I.

MATERIALS AND CONSTRUCTIONMETHODS

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)

4-2

WELLS

4-2.1

GENERAL

Wells make it possible to use the underground
applications
(e.g. water supplies,
irrigation).

water

The quality

depends on:

of the water obtained

from a well

for economical

- 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
process.
Fig.

of the subsoil

which influences

the natural

filtration

The quantity

vatmahod

Point

suriaa

Point

subtrrrumaa

ntwahad

of water obtainable

from a well

depends on:

- The intake area: It is important to realize
that the topographical
does not necessarily
correspond with the geological
or hydrological
drainage area. (see Fig. 23)
- The annual rainfall
percolation:
this
(forest,
area, e.g. kind of vegetation
- The perviousness of the ground: this
stratification
and its homogeneity.
- The storage capability
of the ground:
as perviousness
and intake area.
- Type of well:

its

diameter

and depth.

depends on the nature
farm, bush)

basin

of the intake

depends on the kind of material
this

depends on the same factors

4-2.2
Fig.

TYPES OF WELLS
24

Pelw4bla

lzzil

otrrt4

4b4llowwell
deepwall
01 artaaiianwrll

b -

fipprrumablr rtmta

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.

I’,p;
i l’

4-2.3
1

SITE OF' WELL

It is not always easy to determine the site of a well. Only test
but in general in large plane
boreholes could give certain
information,
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
The site should be also placed in a well
construction.
avoiding the vicinity
of overhanging trees.
Fig.

Siting

to prevent

poilution

= bad site

for

suitable

site

latrine

flow direction

The site of a well
of pollution.

phases in well
drained ground,

shallow
for

well

shallow

well

should be upstream of any possible

source

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

The site should be carefully
chosen.
any possible
source of contamination.
should be avoided if possible.

from 90 to 300cm. It

It should be at a good distance from
Areas known to contain rock layers

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
permanent material
it is a protection
after completion.
construction
thus
of collapse which
concrete is usually

af wells sunk into consolidated
rock, a lining of
is always necessary. This lining
serves several purposesr
it retains
the walls
against caving in and collapses,
It is better to build a permanent lining already during
avoiding the expense of temporary supports and the danger
may occur when the temporary lining
is removed. Reinforced
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?
are
caissons should have a height of no more than 50cm. These caisson-rings
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)

Fig.

hrkinq

method for

a dug- w&J

1. Digging as deep as
possible,
according
the soil conditions

2. Concrete

lining

3. Digging as deep as
possible or until
the water-level
is
reached

water-pi
--L-L-

4. Concrete

lining

5. Lowering of caisson
digging continuously

ring,

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.

Precautions

The following
accidents.

during
points

Most of the accidents

collapse of walls
lined properly

the construction
are very important.
in a well

which are not

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

They should help to prevent

are caused by:

Falling

into

the well.

Sudden collapse of water1
danger of drowning

--I

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.

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.

HAND PUMP

WASTE

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.

WATER

MARGELLE

AQUIFERE ZONE
AT LEAST 2m
DEEP

link

4-2,4,3

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).

WORKING ORDER

CONCREtE RING
(WATERTIGHT)

WATER TABLE

CONCRETE RING
(POROUS)

SINK WELL

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.
of three men is sufficient
for sinking
5 cm diameter and 15 m depth. Bigger diameter
more people.
A team

a tube well
and greater

of a size up to
depth require

Procedure

of sinking:

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
up and
(see Fig. 28a). Move the lever in order to have a perpendicular
down movement. The pipe will sink with these movements provided it is
filled
with water.

Once

the next pipe element is screwed to the first
The sinking continues;
and so on, until it reaches the water table (see Fig. 28b and 28~).

one

If pressure water is available
and can be fixed directly
to the top of
The structure
of the
the pipe, the sinking can be done much faster.
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

Fig.

28 c

Fig.

28 e

---

__---

-- low&

w&r

table
-

-m-w---

4-3

SPRING

CATCHMENT

General description
4-3.1

of springs:

See chapter

2-1.2

'Springs'.

QUALITY AND QUANTITY OF SPRING WATER

The quality
continuously

of spring-water
depends on factors
flowing spring:

similar

to those

in a

The thickness of the stratum which covers the water-bearing
soil:
is important to prevent indirect
contamination
(e.g. from latrines,
fertilizer).

The perviousness

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.

influences

the natural

As continuous flow and quality
take the relation
between

of a spring

spring

capacity

in the rainy

spring

capacity

in the dry season

as a criterion

for

filtration

this

process.

depend on the same factors,

season

the quality

and quantity

5 for good springs

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

constructio

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.

4-3.2

LOCATION OF SPRINGS

We distinguish

three

Grass-land

zones:

Forest

springs
In grass-lands,
inside raffia
bushes.

Volcanic

are mainly

areas

found in valleys

and along streams

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

Where the impermeable

Where two different

Where topsoil

Tracing

appear

stratum

reaches

kinds of subsoil

the surface
meet

meets rock

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
of construction
of a
discover the rising points, where the possibility
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
should
the yield of the spring over the whole year. Special attention
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
it is, proved that short connection to the
of the water is discovered,
surface does exist and that accordingly
the spring is certainly
not of
reliable
quality.

4-3.3

CATCHMENTAREA

The catchment area includes
catchment and may drain into
protective
zone. The radius
depends on the depth of the
covering stratum. The radius
spring catchment is and the
at least 50 m.

the area which is situated above the
as
it. This area has to be established
of the protective
zone from the catchment
spring catchment and the nature of the
should be the bigger the shallower
the
more permeable the covering stratum is, but

no fish
Within this area strictly
no farming, no domestic animal grazing,
no
rubbish
pits
(oil),
no
stables
or
houses,
etc.
are
allowed.
ponds,
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
4-3.4.1

SPRING CATCHMHNT
General

A spring catchment has to be constructed
depends on the topographical
situation,
the type of source.

in a simple and practical
way. It
the structure
of the ground and

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
water pollution

has to be carefully
built to avoid the possibility
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
it is necessary to make special protective
possible to cover it properly,
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
catchment

in a spring

catchment:

pipes or a channel

The actual

(perforated

The supply pipe to the inspection

The inspection

chamber (not to be confused

The inspection

chamber has two parts:

with

Spring

catchnent
ORAIM

- Lau-out
FOR SUlFhCE

WATER

MAllUS FOR CATCNMENT OIRECTION
MAIN

8OUNDARY

MARUS

FOR

FOR .uJRFRCE WATER

PROTECTIVE

ZONE

rr1 r

ORAIM PIPE(IF NECESSAIIY)

SUPPLY

PlPE

.-I

the storage

tank)

installation

The purpose of the inspection
chamber is to control
quality
(sometimes by sedimentation).

with dry walls)

chamber

an entrance basin for the water and
an operation chamber for the appropriate

Fig.

built

water quantity

and

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
and to design and construct

to interpret
the flow of the source underground
the catchment accordingly.

a) Excavation
Normally the digging on the source is started
comes out of the ground. While following
the
ground a drain has always to be kept open to
is required to avoid any increase of pressure
ground and hereby forcing it to find another
controlled
anymore. Moreover, this provision
have a clear picture of the direction
of the
The few following

on the point where the water
flow of the source into the
ensure a free flow off. This
of the source inside the
way out which may not be
will enable the technician
to
flow of the source.

examples are given as a guideline:

Example 1:
The amount of water coming out at the mouth of the trench decreases
digging. Therefore,
water is entering on one or both sides along the
In this case the trench has to be split up in a V or T shape to the
sides as soon as the cover on the mouth of the trench is big enough.
way the bypassing water may be caught behind the dam with sufficient

with
trench.
two
In this
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).

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:
The distance between the catchment
to be sure that no roots can enter

and any tl ? should be
the catchment.

large

enough

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.
-

A“,
I'

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
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
water-tight
Compare with

Fig.

30 Spring

cover

which

figures

of the darn should only be to the height
is on top of the drainage.

30 and 31

catchment

in line

4
IMPERMEABLE
STRATA
WATER- BEARING
SOIL
COVER OF WATER BEARING
BED PLATE
l-2
x
DRY WALL
SLABS
PERFORATED
PIPE

of the

5 6

SOIL

6
9
10
11
12
13
14

GRAVEL
WATER-TIGHT
COVER
DAM
PERMEABLE
MATERIAL
IMPERMEABLE
BACKFILLING
SUPPLY
PIPE
2 x
DRAIN FOR SURFACE
WATER

PLAN

CROSS- SECTION

CROSS - SECTION TYPE 2

TYPE 1

11
9
6

,
,’

Fig.

Spriklg

SECTIONAL
ELEVATION ------v-

ca tchtnent

in shape of a T

-I_--

---

-I_--

5
1
2
3
4
5
6
7

IMPERMEABLE STRATA
WATER- BEARING SOIL
COVER OF WATER-BEARING
BED PLATE (l-2
X J
DRY WALL
SLABS
PERFORATED PIPES

8
9
10
11
12
13
14

SOIL

-’

6 9 11 12

GRAVEL
WATERTIGHT COVER
DAM
PERMEABLE MATERIAL
IMPERMEABLE BACKFILLING
SUPPLY PlPEs(2 L)
DRAIN FOR SURFACE WATER

CROSS-SECTION

COLLECTION CHAMBER

- -

-.-

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
or an entrance.
Ventilators
and manholes
combination with a drain-pipe
should not be directly
above the water , they should rather be placed in
the operation room. Entrances or manholes should be 50 cm above groundlevel with door-steps
at 25 cm. Manhole covers should be locked to
prevent unauthorized
Persons from opening them. It is advisable to cover
entrance) and all openings (incl. overflow and doors)
the chamber (incl.
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
the maximum spring capacity

and drains have to be capable of draining
without restricting
spring flow.

off

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
in stone masonry may
building
materials
for spring catchments. Buildings
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

_'
I'I',,

WATERPRODF PLASKRING
INTERNAL AND EXTERNAL

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.

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‘.

ENTRANCE
( min.Wx70cm)
-

FROM LOWER

VENTILATION
(WITH WIRE NET )

/’

.’
/’ ,’
,I’
/’

SUPPLY PIPE
TO U3NSUMER

,/’
t 2

2
1

CREST- WEIR
I

I
II

,’
/7lt

=-====L
DRAIN PIPE

FROM UPfJER
SPRING CATCHMENT

.’ .’ / ,,” ‘, /,/

‘,‘,,

1 ,-VENTIATION

DRAIN PIPE

1
2
3
4
5
6

cleaning pipe entrance basin
cleaning pipe collection
basin
main valve
ball-valve
for upper source
overflow entrance basin
averflow collection
basin

7
8
9
10

baffle plate
strainer
climbing iron
aeration pipe

x = operating
ball-valve

height of the
+ 30 cm

4-3.4.5

Outlet

The outlet
inspection

Fig.

buildings

building
has to prevent
chamber.

animals

the

Simple outlet

-II?&,

FAVMNT

Fig.

to enter

35 Siphon outlet

a--

WI-

WlT+l Bb- --

’

Commonmistakes

4-3.4.6
Fig.

on spring

catchments

permeable cover

leakage from pipe joints

covering

no surface

chamber cover should be above ground
level

position

of overflow

position

of oulet

no wire-mesh

over the spring

surface
is inadequate

water can pollute

the spring

water

water drainage

too high

covering

the overflow

obstruction
animals
pollute

to spring

flow

or dirt can
the spring water

4.4

WATERPOINT

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

improvement of the quality

hcxage

of water during

gives

two main advantages:

of the water
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

CONSTRUCTIONOF A WATERPOIWT

normally consists of a storage chamber and a washThe water point itself
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.

Small water point

= EFFECTIVE STORPGE VOLUME

(INTO WASH BASIN 1

PIPE

Fig.

38 Large water point

= EFFECTIVE STORAGE VOLUME

SPRING
I,
CATCHMENT

SUPPLYPIPE

. .STORAGE TANK1 DISTRIBUTIONPIPE

. , WASH
BASIN

BARRAGEAND RIVER INTAKE

4-5

In the construction
of a barrage its size, height and foundations
determined by the stream, its bed and its embankments.

are

For our purposes the barrage does not retain water for storage and later
but is only built to assure
consumption (dry season, weekly variations),
the supply. It should be perpendicular
to the streambed. Special attention
is needed for the foundation
to guard against:
-

4-5.1

seepage
washouts, leakages
extensions of the wing-walls
erosion of the river bed

DETERMININGMAGNITUDESFOR THE POSITION OF THE BARRAGE
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

a)
b)
cl
d)

4
f)
9)
i-4
i)

= low speed

V2 = high

deposits of sand,
dirt,
leaves etc.

no or little
settlements

speed

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
by high water or it will
be calculated

Any standing
water behind
water before the barrage,
be as high as possible.

Fig.

Cross section

to the river
cross section
from the flow measurements.

the barrage must be avoided.
The speed of the
in the spillway
and along the sidegate
should

of a construction

in concrete

IMPERMEABLE

Fig.

Cross section

(Ar)

of a construction

STRATUM

in stone masonry

RMCABLE STRATUM

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.

Intake

Construction

lntdke

chamber

-.AB

- SpillWdY

w 3

GROUNOPLAN

---em--

SECTION A -A
HWL . High
LifL - Low water
Udter

sedimentation

level
level
cleaning

pipe

SECTION B - B
intake

chamber

retaining
or

stone

wall

4-6

WATERTREATMENT

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
to
of treatment
processes which the community concerned can ill-afford
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.
for Rural Areas and Small Communities"
WHO)
(partly
from "Water Supplies
all the water supplies
constructed
in the Technical
Section
Furthermore,
of CD/SATA-Helvetas
apply to the WHOStandards of untreated
water (see
this water quality
as sufficient
for any rural
chapter 2-2). We consider
water supply.
In a future
step chlorination
can be introduced
easily.
Treatment
calculated
4-6.2
4-6.2.1

stations
(sedimentation
and slow
sand filters)
for con:inuous
fl% over 24 hours in stage I

are normally
(see 4-l.:').

SEDIMENTATION
General

Definition:
than water

definition

Sedimentation
by gravitation

is the removal
settling.

suspended

particles

heavier

In the rainy season the erosion
of the land by run-off
Natural
existence:
from rain-storms
carries
vast amounts of soil into streams and other watercourses.
Some of the eroded particles
are heavy enough to settle
when flood
often to be picked up again and be redeposited
further
waters subside,
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
in a special
-

Plain
fluid

suspended particles
are removed from raw water
tank. There are three kinds of sedimentation:

sedimentation:
by gravitation

by ser.iimentation

The impurities
are separated
from the suspending
and natural
aggregation
of the particles.

Coagulation:
aggregation
substances

Chemical
impurities

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

Chemical substances
are added to induce
and settling
of finely
suspended matter,
and large molecules.

or hasten
colloidal

precipitation:
Chemicals are added to precipitate
out of solution
by changing them into insoluble

dissolved
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

4-6.2.2

Design

remarks

refer

of sedimentation

to plain

tanks

Sedimentation
tanks are designed
so as to permit suspended solids
The raw water

(of rivers)

sedimentation.

to reduce
to settle

contains

the velocity
of the water flow
out of the water by gravity.

impurities

of three

Particles
large enough to be strained
settle
gravitationally
in still
water

Particles
of microscopic
or colloided
form which
still
water and are too small to be strained
out
required
to remove these substances)

Substances held completely
can be removed by chemical

a) Factors

affecting

settling

velocity
-----I!

drag

force

concentration
wall effect)

---F-I---1

of suspended

or which

will
not
(filtration

dissolved

kinds:
will

settle
is

in the water

efficiency:
7

out of the water
(sedimentation)

in solution,
i.e.
treatment
only.

sedimentation

physical

solids

mass density
of suspended particle
shape density
of suspended particle
mass density
of the fluid
viscosity
of the fluid
shape of suspended particle
velocity
of the fluid
viscosity
of the fluid
mass density
of the fluid
in the fluid

(settling

hindered

The only factor
velocity.
The
is the velocity
depends on the
sedimentation
need less flow
top-soils.
The efficiency

which is altered
by plain
sedimentation
is the fluid
smaller
the size of the particles
removed, the smaller
of the fluid.
The reduction
in flow velocity
needed
nature of th*: sediment and the required
efficiency
of
(e.g. gritty,
granitic
or
volcanic
sediments being heavier,
velocity
reduction
to deposit
them than fine lateritic

depends

also

on design:

inlet
and outlet
prevented;

have to be constructed

so that

short-circni

agitation
of settled
solids
from the sludge zone has to be prevented.
Hence certain
relations
between length and depth are needed,

ting

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.

Calculation

of the

required

dimensions

The dimensions
of a sedimentation
load and the period of detention.
"Surface
SL =
In the
s,

load"
Entity
surface
reverse
quantity
surface

is the

tank

settling

of water
of tank

velocity

p er h

we can calculate
of water_eer
load

can be calculated

of the particles
m3
m2 x h

the necessary
h

(quantity

m3
-xh
h

water

per h)

surface

m3/h
m/h

(period

in the water:
m
h

as follows:
m2

The capacity
or volume of the basin can be calculated
of water per hour and the period of detention:
v

from the --surface

with

the quantity

of detention)

=m3

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 viceversa).

The figures
SL

below,should

only

be taken

as an approximate

surface Load max.
(0.6 m/h is the settling
of 0.01 mm)

= 0.6 m/h
velocity
of' a silt
= 4 - 6 h

of detention

value:

grain

with

a diameter

periode

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
the depth of the tank.
The smaller
the surface load the better

with

the surface

load

and not with

the sedimentation.

Example:
quantity
of water
surface load
period of detention
relation
between length
therefore:
necessary

surface

capacity

and depth

depth
length

width

= 20 m3/h
= 0.6 m/h
= 4h
5 :l
=

20.0
0.6

m3/h
m/h

33.3 m2
====z====

20.0

m3/h x 4 h =

80
m3
--------___------

80.0
33.3

m3
m2

5x2.40m

33.3
12.0

m2
m

width
= 2.70
____-_--_------___-------------

length
=
12.00
m
======================

2.40

12.0

=
m

2.70

= 2.40 m
depth
______---------_------------_--

= 2.40m

LENGTH = .12.00

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

Inlet

zone

is much easier

Outlet

its

bottom

has

zone

i
i

min
max

= 3%
= 8%

and outlets
-Inlets
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

inactive
therefore:

period
reduced

These disturbances
temperature about
Well designed
temperature.

inlets

warm)

zone

of detention

shorter

efficiency

appear already
l/l0

(inflow

with very little
to 2/10 OC between inflow

and outlets

differences
and tank-water.

reduce the influences
87

of the water

Fig.

Inlet:

Variant

1
PREFABRICATEDSLABS

Vl (: 1.0 m/s

Fig.

Inlet:

VO s 1.0 m/s

A good working

V2 -c 0.3 m/s
OUTLET UXS

Variant

Vl e 1.0 m/s

inlet

V2 c 0.3 m/s

shows a horizontal

calm watersurface

in the gutter

Fig.

Outlet

BAFFLEPLATE

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

SLOWSAM) 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
7,25 m3/m2 day (filter
velocity
0,3 m/h) or less.

4-6.3.1

charge of

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

2nd stage

= decomposes plankton
chemical reaction

and the filtrate

3rd stage

= bacteriological

In order
be paid

to guarantee
to achieving:

strainer
becomes oxidised

filtration

a good bacteriological
for bacteriological

filtration.,
reproduction

attention

should

favourable

conditions

and digestion

slow filter

velocity

raw water quality
(pre-treated
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.

by sedimentation

only,

no chemical

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
First,
we treat the raw water by
time of a filter
as much as possible.
the filter
charge in such a way
sedimentation
and secondly, we regulate
Flow into the sedimentation
basin
that no unnecessary water is filtered.
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:

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.

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
System a) :

in the sedimentation

steadv flow

L-,---l

control

tstorage

I
of filter

A overflow

tankioutlet

System b)
steady flow
stor'age
control

of filter

inlet

tank.

tank

4-6.3.3

Size and number of filters

The size
equation:
S

of the filter1

bed can easily

S =
Q =

v =
The ratio

of length

surface
quantity
velocity

to width

be calculated

witn

the follqwing

m2
of water per h or per day, m3/h or m3/day
below 7.25 m3/m2/day or 0.3 m/h

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
Filter
velocity
Surface

required

=
=

20m3/h
0,3m/h

a) Chosen: 2 filter
beds in action
plus
Hence the dimensions
are as follows:
A per filter
chosen width

Total

filter

=
=
-

surface

one stand-by

67m2 : 2 = 33,5m2
3m
33Am2
=
11,2m
3m
(incl.

stand-by)

b) Chosen: 3 filter
beds in action plus
Hence the dimensions
are as follows:

Total

67m2

= 3 x 3.0 x 11,2
one stand-by

A per filter
chosen width

=
=

67m2 : 3
2,5m

22,5m2

length

22,5m2
2,5m

9,Om

filter

surface

(incl.

stand-by)

= 100,8m2

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.

4-6.3.4

Construction

Fig.

Filter

details

bed construction

mu. WATERWm.

WATER
f

;_-

*. . . ',.

.. . : .

mu SAND LtvtL

SAND B0.~-1.oomm
SScm. Or SIN0 CAN BC

RfMOVfO

FOR CLfANlNG

min. SAM0 LtvLL

GRAVEL
5cm B S-lfmm
15cm P15-40mm
10 cm HOSLABS

Fig.

46 Filter

lOmm
Scm

long section

CONCRETE SLAB OR

ClVERFUW
LEVEL
SED.TANK

r’ /J

SLABS WITH SPACE2 cm-l

Fig.

47 Filter

grou~$plan~

OUTLETTo THE
WEFwm ROOM

Fig.

48 Filter

bottom

. .
. . .
.. .
‘.
. * v
_, r.
..- _- . .
*.
3’
‘00
*-ie
)e
: 06)
I

,:,’
,’,’
Lmr
-L, ,.’

:!::,‘;’
:,:i I,,. , ‘(

cross

.
.

-.
.
.

.,.
‘.

..--

l *
.

section

. .

-_.

*
.

-*,.

,.
:A.-;.

o’er0

-..:
. . .
.
.

*
b

\--..*

@l :e\.’ I

’

L CEMENT

BLOCK

L SLABS 60&40/5cm
SPACE 2cm

Fig.

Inlet

gutter

details

GROUND PLAN

ALU PROFILE

-1.00 = MAX. SAND LEVEL
I
1
i

SECTION A -A

CLEANING PiPE

Li ‘Lb-

MIN. WATER LEVEL
w

MAX. SAND LEVEL

WOODEN BOARDS, TO BE REMOVED
ACCORDING TO THE SAND LEVEL

1” CLEANING PIPE

SECTION B-B
95

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 sandfilter
(144 m3/m2/day for tropical
areas only).
Rapid filters
work on
other principles
than those of a slow sand-filter.
There is no "Schmutzdecke" 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
vision
to be adopted

generally
require
in rural
areas.

too much maintenance

and super-

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
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
loss
place, as is the case with an open rapid gravity
plant
(friction
1 m to 3 m).

4-6.5

TREATMENT STATION:

Lay out
storage
Fig.

LAY-OUT

for one sedimentation
tank,
tank (collection
basin).

two sand filters

Hydraulic

system - ground plan

According

to system bl in chapter

3TG?AGE TANK

4-6.3.2

FILTER 1

FILTER 2

SEDIMENTATION TANK

(the cleaning
1
2
3
4
5
6
7

pipes are not shown)

inlet
outlet
ball
inlet
outlet
inlet
outlet

to sedimentation
tank
of sedimentation
tank
valve (depending on storage tank water level)
to slow sand filters
of slow sand filters
to storage tank (collection
basin)
of storage tank (supply to consumer)
p&
valve
0 overflow
I idle pipe
s steady flow
See section

in Fig.

and one

SLOW SAND FILTER

SEDiM~NTATlON TANK

OPERATION ROOM

STORAGE TANK

MtN. WATERLEVEL.

C
7’

, ,’

_-.
rCllLICICL--.*->-1C&31.

,..

. .

. .
:.
..
..
_ .

*. _

..*
.’

1
2
3
4
5
6
7

inlet
outlet
ball
inlet
outlet
inlet
outlet

sedimentation
tank
sedimentation
tank
valve
slow sand filter
slow sand filter
storage tank
storage tank

0
I
S
C

overflow
idle pipe
steady flow
cleaning pipe

W valve

(Ground plan

see Fig.

50)

4-7

STORAGE

4-7.1

GENERAL

The necessity
points:

of providing

a storage

tank

is depending

on the following

continuous
supply
A storage tank has to be provided
in case the source's
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)

In case the continuous
supply of the source is sufficient
to cover
no storage tank is required.
peak demand of the consumer, generally
the supply pipe from the source to the consumer has to be designed
peak consumption.

Between the critical

4-7.2

cases a) and b) are many other
/

possible

the
But
for

cases c).

CAPACITY OF A STORAGETANK

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

cases a) to c)

the determination
of the storage
(as described
above) are shown:

tank

capacity

for

the

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
area of the United Republic
of Cameroon:
a village
in a rural
30 % of
10 % of
35 % of
20,% of
5 % of

the
the
the
the
the

day's
day's
day's
day's
day's

supply
supply
supply
supply
supply

between 6am and 8 am
between 8am and 2 pm
between 2pm and 5.30 pm
during the other hours of day light
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)

I ..,

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
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.

1
1

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.

Water consumption
cases of supply.
Lvvw

in a rural

viilage

with

different

coNsuMpTK)N

CASE a)
60 .I.

/df*
ti n’
i i iA

----............

Pig.

diagram
case a)
case b)
case c)

of hourly
consumption
the daily
supply is equal to the daily
consumption
the supply is equal to the peak consumption
storage capacity
required
= cl + c2

Daily water consumption in Nqonzen water
(an other example
of case a)

x
II
100
no _
00 .,
70 .

I
I

100

(grassland)

VW = \6+ v4 = 22st lBZ= 412
INFLOW EOUhL TO DAILY CONSUMPTION
IF IN’FLOWWORE THAN OAILY CONSUMPTY)N
I- THE STORAGE VOtlJMC WILL BE REDUCED my/I

t/ 0i--

supply

4-7.3

DESIGN OF STORAGETANKS

The site for a storage tank should be chosen as close as possible
area of highest consumption.

to the

The minimum water level in the reservoir
should be between 20 - 80 m above
If the level difference
is exceeding
the area which will be supplied.
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
oL the water has
peration must be
There
screens).

be protected
against external
influences.
A good circulation
countries.
to be ensured, due to the warm climate in tropical
provided. Doors and windows have to be insectproof
(mosquito
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
100 m3
100 - 200 m3
200 - 300 m3

Water depth in m
usual
2.00 - 2.50
2.50 - 3.50
3 .oo - 4.00

101

optimal
2.50
3.00
4.00

I,”
i’,

r3.g.

xorage

ianlc construction

IR VENTILATION

- INLE T (El/, WITH

4AU _ VALVE 1
*
iii/

1/1/i

min ZOcm

L/1

-.--‘.--”

DlSTRiWTlON

DISTRIBUTION SYSTEM

4-8

The aim of the distribution
system is to transport
the water safely
from the main pipe to different
places of consumption,
such as standshowerhouses,
etc.
pipes, wash-places,
4-8.1

LAY-OUT OF THE DISTRIBUTION SYSTEM

When designing
a distribution
points have to be considered:

system of a water

the advantages
systems and

and disadvantages

the subdivision

of the system

4--8.1.1

Types of distribution

a) Branch

system or dead-end

supply

of the different
into

different

the
types

pressure

following

two

of distribution
zones;

necessary.

systems
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
connected together
with the result
that the circulation
and the possibility
of stagnant
water is reduced.

the dead-ends are
is much better

103

dead-ends

cl Ring
system
.
In this system the distribution
advantages are considerable:
-

4-8.1.2

main is connected

as a ring.

The

good circulation
of the water
safe in case of breakdowns
supply not interrupted
in case of repairs

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

4-8.1.3

Disposition

of taps

Public standpipes
requirements:
a)

population

technical

and wash-places
concentration:

considerations:

are installed

,“;!:
,, ,‘.
,, ., 2 ;
1,
/,.A

!” y

to the

following

not more than 80 - 100 persons per tap;
no one should have to carry water mere
100 to 150 m
cleaning

104
8’

according

and aeration

than

4-8.2

PIPING MATERIAL

4-8.2.1

General

There are three
it
it
it

a)
b)
cl

for

must convey the quantity
must resist
all external
must be durable

In order
pipelines
-

requirements

to &al with this
into the following

a pipeline:
of water required
and internal
forces

subject
adequately
categories
which

it is necessary
to classify
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
their
main functions:

a) "supply
(spring,

mainsW for the conveyance of water
river,
lake) to the storage
tank;

from the water

b) "distribution
or service
mains" are, as their
name implies,
mains" frorr. which individual
house supplies
are tapped;
cl

"gravity

d) "pumping
-

mains"

These last

rains"

the physical

two classifications
working

source
the

"street

are made to specify

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
they give alternative
means of feeding an area when shut
repairs
are necessary
they avoid stagnation
of water at dead-end of main

"Service
a village

pipe" is the supply line,
laid under ground
section
quarter,
a house, or a farm.

"Plumbing pipes" are pipework within
of water to the various
appliances.

The following

types

of pipes

are in use for

Applicable
cast iron pipes
---_-__.* .-.- -.- _
asbestos-cement
pipes
.~
galvanized
steel pipes
-----.- - ._.___. .._..___.
bitumen coated steel pipes
--prestressed
concrete
pipes
,._.-.-.,. _
plastic
pipes (PVC + PE)
.-.
_I
copper pipes

= applicable

a building

applied
in CD/SATA projects
in special
cases only

Trunk

for

frcm a main to

the distribution

the construction

main

Service

system
downs for

pipe

of mains:
Plumbing

X
X
0

in Cameroon

pipe

‘,‘”

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
in pressure
classes 5, 12, 20, 25 and 30 kg/cm2.
The classes denote the test pressure
manufacturer's
wcxks. The tightness
pressure of the pipes.

of 50 to 1'500

in kg/cm2 of the tightness
test in the
test pressure
is twice the working

Pipes are marked in the customary way, e.g. a pipe of 250 mm inside
designed for a working pressure
of 10 kg/cm bears the code:
Durabest
Couplings

are similarly
6

All

pipes

class

250,

coded,

250,

are tested

class

at twice

mm and

diameter

20
i.e.:
20
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-SATAHelvetas 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
advantages compared to
resistance
towards all
their
light
weight and
The raw material
for
is Polyvinylchlorid
The plastic
pressure
(PE) mixed in powder

and plastic
pressure hoses offer
considerable
pipes made of &her material,
due to their
great
known aggres,ive
matter
(see chapter 2-4.41,
to
their
easy handling.

plastic
pressure
pipes (e.g. Symadur pressure
pipes)
(PVC) in powder form.
hoses (e.g. Symalit PE-hoses) are made of Polyethylene
form.

Much attention
has to be paid tc an adequate fabrication,
Plastic
pipes for
be fabricated
according
to
the purpose of transporting
drinking
water must
A well equipped
established
regulations
(e.g. in Germany: DIN 19'532).
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

);

The following
explanations
are based on many years
factory
internal
experience.

international

and

Transport:
it is essential
that the bottom row of
When transporting
plastic
pipes,
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
The pipes must be stacked on
to cover them during
long stacking
periods.
The manufacturer
advises to use wooden'batons
at the base
an even surface.
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
They are supplied
in straight
service pipes and can sustain
high pressure.
length of 6 m.
Note :
Only untreated
bent to curves
will
start.

pipes (black)
the protection

can be bent to curves.
may get cracks where

If treated
pipes are
in due course corrosion

Steel pipes may be supplied
black (untreated)
or galvanized,
or bitumen
coated inside
and out, or additionally
sheathed on the exterior
with glass
compound. They have screwed
fibre cloth and a further
coating
of bituminous
A great variety
of special
ones
ends and are connected by steel couplings.
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
sluice

for

valve

tight
(gate

plug valve
--.. . ---._--.-.--__
butterfly
valve

valve
.. .._

screw down plug valve
(stopcock)
-.--.
_.
non return
valve
control
pressure
4,

b),

1) only

closure

flow
--

control
-."

x 1)

valve

special
control

valve

(gate

- 2)

c) and d) are applied
with

control
a)

reducing

pressure

valve

2) pressure

a) Sl;ice

in CD/SATA-Helvetas

projects

in Cameroon

equipment
functions

only

water

is flowing

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
through a pipe because only
closure
has any substantial
pressure
of the water in the

proper device for controlling
the rate of flow
the last 10 % travel
of the gate towards
effect
on the flow rate (depending on 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

1(
'I
',

::'1
:!'
';,',,,I,
i,B:',,,
P',
i'!: ,
,I',,,','
fp;
v;,,:: 5'
q,;<
,~_)
g;y,' I_,
$,‘ I
Li'
i':.,,,a,,

Fig.

of friction

Diagram

Pipes

according

k = 0,l

loss in galvanized

steel

pipes

to DIN - Norm 2440

mm
the inside
diameter d

The nominal
diameter ND
3/Ofb

10 mm

12,5 ma

l/2"

15 mm

16,0 mm

3/q"

20 mm

21,6 mm

25 mm

27,2 mm

11/4"

32 mm

35,9 mm

1 l/2"

40 mm

41,8 mm

2"
21/2"
3"
4"

50
65
80
100

or
or
or

mm
mm
ml
nun

53,0
68,8
80,8
105,3

mm
nun
mm
mn

IOMnin

IlOI/min

200

300

500

100

XXII/mm
100*/w

I ‘.

678

QUANTI’TVOF WATER ( llmin 1

200

“”

1%a

,‘,I’

500

lea

It is quite
economical.
Trunk

main-lines,

stage

Main-lines
stage

stage

supply

velocity
in the pipes is most
give a general
guideline:-

pump discharge
stage

v = 1.0 m/set

of air

pipes
v = 1.S m/set

connections

stage

v = 1.5 m/set

stage

v = 1.8 m/set

pockets

The presence of air in a water main can cause serious
wren when the main is of a large diameter.

blockages

to the flow

Air

pockets

a)
b)

where the static
head on the pipe is lower than 5 m
by high points
in the pipeline
and where the pressure
in the pipeline
decreases
(compared to the hydraulic
gradient)
by operating
a pipeline
with insufficient
means of aeration
when
the flow capacity
of the pipeline
is bigger than the inflow

c)
d)

can be caused:

The minimum pressure
Fig.

- 2.0 m/set

main

v = 1.0 m/set

Prevention

water
should

house or stand-pipe

or service
I

main,

v = 0.8 m/set
without

Distribution

4-8.3.2

clear that a certain
The following
table

in a pipeline

should

be at least

5 m.

hydraulic

gradient

at least

--correct

hydraulic

diameter

gradient

Fig.

Longitudinal
section
showing desirable
valves on a length of pipeline
-.

Point
Point

gxadient
-.-.-,

Arrows show the possible
of the air accumulation

a: Air likely
to accumulate
and steeper downgrade in
b: Lessening of upgrade in
of air
c: Summit; large air valve

because
direction
direction
for

of lessening
of flow
of flow will

filling

hd *
special
aeration
because

Fig.

for

air

-.-

-.-.-

desirable
positions
for air valves

A low point with
cleaning
pipe
Point

static
-.-.

-.-.-.

positions

case:
in point
hd * he

Hydraulic

purposes

direction
(-)
of hydraulic

cause accumulation
will

be required

profile

correct

wrong profile
116

gradient

profiles

- 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
A
hydraulic
gradient
existing
on the main. (Fig. 60 shows an example).
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
An air valve must also be inserted
rise there must be an air release valve.
and then changes gradient
so as to rise less
where a pipeline
rises steepl?!,
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
pipes taken above the static
gradient
can be
low heads, open-ended vertical
used instead of air release valves,
provided
precautions
are taken to prevent pollution
of water.(Compare
with Fig. 62)
It should
the water
erratically

be kept in mind that air does not necessarily
move forward with
but may move backward against
the flow of water,
slowly or
(waterhammer).

- Before a pipeline
can be filled
with water
releasing
air from it. Once 'the pipe is full
for release of air must be closed so that no
high points
should be open as long as air is

, means must be provided
for
of water, however, any aperture
water is lost.
Ventilation
on
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 outflowing
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
but blockages
to flow can happen with hand-operated
air
because air pockets can build up in a very short time.
Special case of air
hammer:

pocket

which

reduces

the

flow

rate

correct
117
--.

release
release

valves,
valves

and can cause water-

Prevention

4-8.3.3

of vacuum

Vacuum can be caused:
-

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.
There

is no doubt that in a well-planned
supply system a vacuum caused
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
it is important
to install
automatic
anti-vacuum
high points.
Therefore,
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).
a)

by dropping

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

Fig.

Air

release

Automatic

valves

and anti-vacuum

valves

valves
STATIC GRADIENT
--

Ventilation
pipe min. b 1"
with return
bend and sieve to
prevent pollution
of water
caused by animals or dirt
Open ended pipes taken above the static
air release or anti vacuum valves.

gradient

-cleaning

pipe

can be used instead

(with little
steady flow}

ENTILATION

AIR

- REGULATOF

DRAIN

LARGE AIR VALVE ’ w
FOR fll.LlNC OF PIPE
-LINE AT
HIGHPOINTS 0I-iY - --

118

VALVE FOR
MAINTE NANCE

Fig.

Intermittent

ventilatiofi

‘a)

stand

The ventilation
valve
pipe-line
(prevention
(a) Also

Fig.

64 Anti

regularly

has to be opened from time
of air pockets)

used standpipes

can prevent

air

to time

pockets

to ventilate

at high

pipe

the

points.

vacuum valve

After closing
the main valve
(prevention
of vacuum).

the ventilation

valve

must be opened

VENT11.ATION
VALVE
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
ground-water
could enter
they are sited.
If this is not done, then polluted
The pit in which the air valve is sited should
the main if it is emptied.
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
crossings
should b<)

laid along the straightest
route possible.
Road
ne at a right-angle
to the road whenever possible.

rise of about 2%
Every length of main should k,: laid with a continuous
so that air can be released
through air valves,
or
to 5% to high points,
where a cleaning
valve should be
with a continuous
fall
to a low point,
of pipelines,
fixed for emptying
&at portion
of the main. Flat lengths
or those laid parallel
with the hydraulic
gradient,
should be avoided
since they may give air-lock
problems.
Changes of direction
-

flexible
)ling

r:iid

TiZ”;.

F‘
r

should

be made, whenever

such as Viking
joints,
for A/C pipes allowing

joints

using

Johnson
gradual

prefabricated,

flanged

.ed steel pipes should not be bent into
It would
ctive coating
may get cracks.
3 with screwed joints.

possible,

coupling
deflection

For other

Note:
allow

joints

recommended for

- according

for

or screwed

steel

asbestos

pipe

pipes,

the internal
to remove

be done along the
out after
the pipe

is $ = 50.

(5O = 9 cm

to the manufacturer

the trench has to be wider at a bend than along a straight,
space needed to complete the above pipe-laying
instruction.

120

or RK

bends.

curves because
be very difficult

drtion
of pipe into a coupling
should preferably
the shift
being carried
itxis of pipes already
laid,
has been inserted.
The maximum deflection
offset/m
length)

by using:

- DOTTohi
COIIRCCT

DOTTOM

PLANNED TRCMH

depends

I:',

IOTTOW

TOO HIGH

soil

type

and conditions

cost

considerations

The recommended economical
at least
a = 60 cm.

on:

width

of trench
121

at pipe

level

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
the water temperature
increases
and
If the pipe is not buried,
trees.
provides
excellent
breeding
conditions
for microbes,
and any tree falling
onto the pipeline
may cause damage. When pipes are laid with more than
investigation
is called
for to ensure that
1.5 m to 1.8 m cover, a special
-ough
to
stand
the
earth
pressure.
If
they
are not the
they are strong I
remedy is to bed or fully
surround
the pipeline
with concrete.
Trench depth like trench width also
costs. All factors
should,
therefore,
excavating
the trench.
Recommended depths

Fig.

through

along

underneath

pressure
\

roads

lines

in different

bearing on laying
very carefully
before

situations

100 cm (min 60 cm)
100 cm

roads

Crossinq

normal

Note

bush

for

has an important
be considered

back-filling

150 cm

of main roads

The pipe should
into a sand bed
covered with at
20 cm sand. The
ning back-filling
done normally.

be laid
and be
least
remaiis

The pipe should be laid
into a sand bed and be
covered with approx.
20
to 30 cm sand. An additional
concrete
slab will
help to reduce the load
caused by traffic.
The
remaining
back-filling
is done normally.

Back-filling
unsuitable

should always be completed
in layers.
as it results
in excessive
settling.
122

Bulk

back-fil

.ling

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
prevent damage to pipes from root growth (moving or
or by uprooted
trees.
This is very important
if the
rigid
couplings
because an uprooted
tree can damage
a rigidly
joined pipeline.

m should
squeezing
pipes are
a lengthy

be cut to
of the pipe)
joined with
section
of

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
to allow an adequate support
for the pipe over

couplings
its entire

the couplings

(rubber

sealing

123

rings)

so as

correct

The pipe
over its

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
weight of the cover
rests on the pipe which
may cause it to fracture
in due course.

wrong

Moreover
leak.

or sockets
length.

may be loaded

is supported
entire
lenght.

unevenly

and

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
material
stones. Once the pipe has been covered with 20 cm of suitable
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
tamping.

may be used where drainage

is good.

Do not

lift

the pipe

while

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.

Back-filling

Place

Tamp soil under pipes and between pipeline
and trench wall at both side. Water
tamping may be used where drainage
is good.

Place

124

soil

up to l/2 external

diameter.

up to the top of the pipe.

Tamp soil
between
at both sides.

Back-filling
by hand until
20 cm over
pipe. Tamp each 10 cm layer.

Bulk-filling

pipeline

and trench

of the remaining

wall

the

trench.

If the pipe trace has not been marked during construction
it will
later
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
to mark the pipe trace permanently:

Fig.

Pipe material

The directions

Continuous

Examples

and diameter

laid

of the pipe

into

information

may be the best

the ground

trace

numeration

in sequence

of markinq

peqs

of all

concrete

pegs.

marks for
direction

pipe

trace

Asbestos cement pipe
gi 200 m
Peg No. 12
(continuous

i ,’
a m llem min

125

numeration)

way

, _,

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
because:

pegs should

generally

be buried

to one side

of the pipe

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.

The material
above the pipe initially
will
and the pegs may sink with any subsidence

ACCORDING TO PIPETRACE
BUT NOT MORE THAN 300 m
--

126

not be fully
and eventually

axis,

consolidated
get covered.

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
attached
to the line,
or it may endanger line safety
down unevenly.

Fig.

Thrust-blocks

required

ig,

73
(d

for

thrust-block

Thrust

forces

area

R
soil-bearing

is not firmly
the line beds

of directions

P in metric

of pipe
mm

changes

tons

internal

power (T

=LxW=A

at end closures:
pressure

p = kg/cm2
10

0.57

0.75

1.13

0.57

0.85

1.13

1.70

0.52

0.87

1.31

1.74

2.61

0.25

0.75

1.24

1.87

2.49

3.73

200

0.44

1.31

2.19

3.28

4.37

6.56

300

0.94

2.82

4.70

7.05

9.40

7.5

0.08

0.23

0.38

100

0.11

0.34

125

0.17

150

127

.lO
--

Factors

for

calculating

Bends:
Factors:

thrust

90°
1.41

Branches

factor

thrus tforce
R = 1,41 x P

0.70

force

60°
1.00

R at bends and branches:

450
0.76

(em&.rically

300
0.52

longitudinal
This

thrust

R= 0,70 x P
= branches
factor

Thrust-blocks

111/4o
0.20

drawn from experience

The thrust-block
at changes of directions
the forces so that the foundation
pressure
soil-bearing
power.

Fig.

221/2o
0.39

for

changes

relies

on its

R=P

in the ground plan distributes
does not exceed the permissible

of slopes

section
block

weight

to withstand

OCCIEing

forces.

The following
calculations
to those for a thrust-block
changes of directions.

are similar
for

Examples

of calculation:

#I125

Example 1:
Thrust-block

for

Water pressure

a branch

d 100 mm
/

= 10 kg/cm2

Permissible

soil-bearing

Out of Fig.

70:

The required
Chosen:

power

P = 1,13 tons,

thrust-block
L = 40 cm
W = 30 cm

0,75 kg/cm2

the

factor

area A =

with

R
r

for

b I100
branches

- 0,70

0,70 x 1130 kg
0,75 kg/cm2

1060 cm2
========

30 x 40 cm = 12nO cm2

Example 2:
Thrust-block

for

a change of slope

Pipe B 150 mm
Water pressure
Specific

= 7,5 kg/cm2

weight

Out of Fig.
The required

of concrete

= 2,4 t/m3

70: P = 1,87 tons,
thrust-block

Chosen concrete

thrust-block

the factor

volume

for
=

0,76 x I,87
2,4 t/m3

of 0,85 m x 0,85

129

45O = 0,76
t =

o 5g m3
I
=======:

m x 0,85 m (with

0,61 m3)

$125

d4.4

Pressure

test

of the pipeline

It is very important
to test the pipeline
before the trench is backfilled
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.

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
In that case, the joints
linking
individual
shall be tested in sections.
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
But at the lowest point of the section
it
of the very pipe section.
should never be higher than 1,2 times the nominal pressure
of the
pipes.
Fig.

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
tight.

pipes,

the pressure

should

be constant

the pipe-line

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.

Testing

For plastic
water hose.

by natural

pipes,

there

slope

should

For A/C pipes,
the refilled
inner surface per hour.

be no loss

amount of water

of water

should

in the transparent

not exceed

0,05

l/m2

Notes:
-

The testing

pressure

shall

last

for

15 minutes/100

The air
pipeline

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.

at high-points
has to be released
with water for the testing.

131

during

m length
the filling

of pipeline.
of the

Valve

4-8.4.5

chambers

It is necessary to have valves at intervals
along a pipeline
which
be used to control
the flow of water. These valves are preferably
situated
in a chamber built
of concrete
or cement blocks.
Fig.

75
c=

Chambers with

min 20 cm for
min 25 cm for

a depth
pipes
pipes

can

up to 1,O m

4 50 and 80
rd 100 and 150

1 depending on the length of
1 the spanner to open the
screw of the joint

a ;: min 6Oun

or 2 x 6 + WTSIDE
& OF VALVE

t
b = min 60 or LENGTH
OF VALVE

Note:

+ 2 x 10 cm

Length of valve always
ventilation
valve.

TEE

PLUS

includes

min10

length

of main valve

and of

OF VALVE

klel
min 30

min 30
4

132

,I.

Fig.

Chambers with

Iir

a depth

more than

1,O m

LENGTH 0F \(ALvE + 2

iocm

Bi OF VALVE

0
@

CLIMBING

60 + c + OUTSIDE
0 OF VALVE

IRONS

CLIMBING

Note:

Length of valves always
ventilation
valve.

includes

133

lengths

of main valve

IRONS

and of

If a pipe
passes through a wall,
it and could damage the pipe. It
stresses
by using constructional

certain
stresses
from outside
is, therefore,
very important
details
as shown.

may affect
to prevent

Rigid connection
applicable
cleaning
pipes or pipeline
a building
only

for
inside

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

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
sand can be glued (with plastic
This solution
allows to connect
pipe end directly
to concrete

of
glue).
this

pipe-line
water
tank
pipe

bridge

working space
during constr uction

expansion/contraction

slip

joints

134

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
-

the
the
food
and

public
public
crops
public

distribution

buildings

are

standpipes
from where the consumers carry water
washplaces where the population
washes clothes,
or coffee
shower houses.

Public standpipes
requirements:

and washplaces

are installed

according

to the

following

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
Fig.

Public

standpipe

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
centres

4-8.5.2

the public
of towns.

fountain

Public

washplaces

is constructed

Fig.

Public

washplace

in concrete

Fig.

Public

washplace

in stone

on market

places

or in

construction

masonry

construction

The standard designs of Fig. 79 and
Fig. 80 are shown in the appendix

136

Fig.

Standpipe

Ground

with

washtable

plan

.L.*

-’
TIE!

A
-.d

wash table

Section

A- A
pipes
:hors

Fig.

Coffee

1.20

wash-place

I
I L
rlevel

1 I I
I-i--i-

Section

A-A

Section

B-B

4-8.5.3
Fig.

public
83

shower housq

Standard

shower house

lbI

roof

I
I

Ground plan

Fig.

(scale

Section

1 :lOO)

Public shower house with
and 2 washplaces

8 heads combined

I
I

I
I
I
I
I
I

pipe

4
I
I
i
I
I

stacking

a fitting

----------l

l-----------I

with

A-A

I
I
I

I
L
I

9
fi

I 4
I i!
I n,
I

I
I
I
I

---

L -------A---

Ground plan (scale 1: 100 1
138

---

-roof

store

WATERLIFTING

4-9

In rural
areas, some
to obtain
their
water
and should always be
start.
It can be said
by gravity,
which works
pumping. The gravity
cost low. The running
high for a commllnity
cases it is inevitable

4-9.1

villages
may be situated
in a way that enables them
supplies
entirely
by gravity.
This is a big advantage
considered
first
when investigations
for a water supply
that it is always
safer to ccnstruct
a water supply
if this is possible,
than one which requires
system needs less maintenance
and keeps the running
cost and maintenance
for pumps can be considerably
which is financially
weak. Nevertheless,
in certain
to install
pumps to obtain
the necessary water.

TYPES OF PUMPS

There are two main types
-

plunger pump (or piston
centrifugal
pump ,

The following
diagram
discharge
and delivery

of pumps which

are suitable

for

water

supplies

pump)

shows the application
head.

of each one in relation

P = Plunger

pumps

C = Centrifugal

pumps

The economical
the application
or centiifugal
the ratio:
(l/see)
H (m)

Plunger

pump:

The most common pump of this type
which water is moved by the direct
reciprocates
in a closed horizontal
Centrifugal

limit
between
of plunger
pumps
pumps lies at

is the reciprocating
plunger
push of a plunger
or piston
or vertical
cylinder.

pump in
which

pump:

The pump-wheel turns with very high speed and centrifuges
outwards producing
the water pressure.

139

the water

Summary:
Pumping systems

type of pumpr
application

driving
remarks

plunger

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
to 5 meters

- hand pump
up

for

of water

pump

centrifugal

other

pump

systems

4-9.2

HAND PUkPS

4-9.2.1

Deep well

high

discharges

energy,

hand pump
driven by wind mill
animal drive
electrical
or diesel
erlgi ne

requires
fast running
drives:
- electrical
engine
- diesel
engine
- petrol
engine
- water turbine

hydraulic
ram
(see chapter 4-9.4.1)

self drive by water
(waterhammer)

hydro pump
(see Fig. 90)

- foot

bucket and rope with
rope pulley
for wells

- manpower
- animal drive
- diesel
engine

pump

pum&

The hand-operated
pump can be usedin
welis of any depth. In those which
is usually
placed
have a suction
lift
of less than 5 m, the pump-cylinder
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
it is best to have the cylinder
in or very close to the water.
the year,
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
lift
;I,

designed
water

deep well

from a deep well.

lift

pump is a simple

and economical
-

solut.ion
to
_----

Fiig, 85 Deep well pump.
construction
and maintenance

needs

_ 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

4-9.2.2

Fig.

reference:

7 (see selected

Bibliography)

Wing pump

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
are normally
not required.
limited
space for installation.
Air vessels
Regulation
is done by the use of throttle
valves.
The connection
to fast
running
engines is required.
Caution-if

the water

The dif,ferent
-

types

contains

sand

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
"Planning
of
Centrifugal
Pumping
Plants"
by Sulzer Brothers
information
see
Ltd, 8400 Winterthur/Switzerland,
or other relevant
literature.
II_ will
always be necessary when designing
a pumping
manufacturer
of the pump and the pump drive as early
planning.
1

system to involve
the
as possible
in the

Pump characteristics:
Each centrifugal
pump has a characteristic
ratio
This characteristic
delivery
head and revolutions.
called
characteristic
line.
The characteristic
line of a pump is
checked with a test installation.
There are pumps with
characteristic
lines:
-

steep characteristic
change of Q results

flat
characteristic
very much even if
a little.

steep

calculated

between discharge,
is shown in a curve
by the manufacturer

and

and flat

line:
small
big change of H
line:
Q changes
H is changed only

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

100 mm

max. 1.5 m/set

0.6 m/set

normally
Velocity
in discharge
high but with this it
Required

pipe 1.5 m/set to 2.5 m/set. This veloci%y
is quite
is possible
to keep lower the costs for fittings.

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.
conditions
have to be checked seriously
if a second plant
run parallel
to an existing
one.

4-9.3.2

The discharge
is installed
to

Pump drives

governed
There are various
ways of driving
a pump. The choice is generally
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
the initial
investment
is quite high,
than other drives.

cost as a pump drive.
Even though
this system is in the long run cheaper

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:

as such an engine is quite
The most common pump-drive
is a diesel
engine,
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.
this drive is not explained
more detailed.
t Therefore,
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
Fuel should,whenever
possible,
to provide
adequate space for fuel storage.
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.

145

4-9.3.4

Data needed by an enquirer

1) Arrangement or as per enclosed
level
................ m
2) Purpose

sketch

No. .,...I....

altitude

above sea

of pump . . . . . . . . . . . . . . . . . ..I...................................

3) Duty of pump
. ........
a) Discharge
in l/set
. . . . . . . . . . . . . . . . . . . . . . . . . . . or cu.m/sec
m liquid
column
b) Manometric suction
head .,........*..*........
m liquid
dolumn
c) Manometric head .,"...........................
(including
manometric
suction
head under 3b)
4) Data for installation
(only
above cannot be answered)
a) Static
Hd '90

or geodetic
head:
= Height between

answer

questions

4a and 4b if

3b and 3c

pump centre

line

and upper

water

level

..... m

line

and lower

water

level

..... m

HS gee

= Height

between

pump centre

H geo

= Height

between

upper

and lower

= Height

between

lower

water

levels

............... m

H max
or
H' max
b) Piping
rd

level

outlet

.......... m

data:
= Inside

diameter

of suction

pipe

diameter

of strainer

and foot

. ..I......
.......... m

= Total length of suction'pipe
L.5
Number of bends in suction
pipe
Inside

and free

.. .... .. ..
valve

. . . . . . . . . . mm

c) Supplementary
information:
..........................................
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..*.........
..,..........~.......................................................
. . . . . . . . OC
5) Water temperature
Specific
gravity
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
or is there a fire explosion
hazard? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- . . . . . .

I
I

i
146

~&:~~.‘,‘,,; . 1 “~
b::. .,{‘, 1 .- ‘: %“’ I
II,.,. .
i,~’
,:,‘.I

b) Other drives:
Petrol engine,
Diesel engine,
steam turbine
.. .... ...... ... ......
If existent:
Power N = . . . . . . . . . . Speed n = . . . . . . . . . . . . . . . . . . . r.p.m.

: ;'I
:'..

‘/
:-

c) Belt drive:
Driving
pulley

Diameter
Width
Speed

. . . . . . . . . . . . . . . . . . mm
. . . . . . . . . . . . . . . . . . mm
. . . . . . . . . . . . . . . . . . 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.
......................
enclose characteristic
curve of pump. IS the
If of other manufacture,
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
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
pump or pumps, how great is the total
maximum discharge
.........
Hmano would then be
.........

fluctuations

an existing
quantity?
. . . . . . l/set
...... m

b) Discharge pipe:
- Total length of the pipeline
............... m
. . . . . . . . ..I....
IMU
- Mean inside
diameter
- 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)
. . . . . . . . . . ..I.....
- Is the pipe directly
connected to a reservoir?
- Is the pipe indirectly
connected to a reservoir
through a
.
....... ..........
reticulation
network?
- Is water
continuously
being tapped along the pipe, and if so,
. . . . . . . . . . . . . ..I..
how much?
c) Existing
equipment to counteract
pressure
fluctuations.
These may be:
controlled
non-return
and discharge
valves,
flywheels,
air vessels,
surge tanks, etc. If any such device is available
air injectors,
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.

Hydraulic

A
C
R
St
Qi
0
S
Ql
Ll
Hl
H2

=
=
=
=
=
=
=
=
=
=
=

=
=
=
=

L2
D

ram

airation
of driving
pipe
collection
tank or sedimentation
tank
hydraulic
ram
storage tank
supply from source
over flow
strainer
at drive pipe
driving
water
length of drive pipe
difference
in elevation
between ram and supply - power head
difference
in elevation
between ram and storage tank to which
water is to be elevated
- pumping head
waste-water
daily
consumption
supply from ram to tank - possible
length of supply pipe
distribution
pipe

similar
to that shown in which
Given suitable
circumstances
- a situation
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
Ql, Ll, HI,

to the manufacturer
about
Q2, L2, H2 is necessary.

Hl
Keep in mind ~2 = 1:4 to 1:8.
(1:4

to 1:5,

ram sizes,

the

information

in items

The drive pipe should have a static
pressure
of max 15 m, if more, we need more stages.
for rams of the make "Blake") .
149

4-9.4.2

The hydro
Fig.

pump

Hydro

pump can be used in wells

90 The principle

of the hydro

of depths

up to 60 m.

pump

i
.

Discharge
---.,
valve closed
L
The sleeve
retracts
Suction
open

valve

----- -

Suction:
The pedal goes up,
the sleeve retracts:
water
is sucked into the stainless steel pump body.

Discharge
valve open

The sleeve
extends

+-----

Suction
closed

valve

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
- the easy installation
of the pump
- the simple maintenance
(all wearing
and are directly
accessible).

are:
parts

are located

Hydro pumps can be adapted
for other types of drive:

hrnd tyos

wlnd whwl lypa

in the pump head

Chapter

Table

ADMINISTRATION OF PROJECTS

of contents

page
153

5-1

TECHNICAL REPOKT

5 - 1.1

The aim of the technical

5 - 1.2

Contents

5-2

EXECUTION OF PROJECT

156

5 - 2.1

Before

starting

156

5 - 2.2'

During

the

5-3

COMPLETEDPROJECT

156

5 - 3.1

Financial

156

5 - 3.2

Final

5 - 3.3

Drawing

5 - 3.4

Document file

of the technical

153

report
report

a project

construction

156

statement

report

and handing-over

file

157
157

of plans
of a completed

153

project

157

5-l

TECHNICAL REPORT

5-1.1

THE AIM OF THE TECHNICAL REPORT

in the various
The technical
report
is an important
document, necessary
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
all necessary
information

interested
and details

in co-financing
a project
in the technical
report.

will

find

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
Emphasis should be put on
main points
that make up a technical
report.
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
and clear information
is
Socio-economical
aspects
(here, detailed
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
Pumping station,
interruption
chamber
Storage tank, other tanks
Distribution
Construction
methods, choice of material

sand filter)

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,
include
the inflation
cost during
the estimated
pipes,
etc.).
If possible,
construction
time.
Cost

in cash:

a) Buildings
Catchmant
Sedimentation
tank (Or interruption
Storage tank
Stand pipes, wash basins
Shower house & store
b) Hydraulic

tank)

installations

Pipes (plastic,
galvanized,
asbestos,
Pump with driving
engine (motor-pump)

etc.)

c) Sundries

& hydraulics)

(10 to 15 % of buildings

Transport
Tools, lubricant,
Contingencies

spare

Parts

Cost in kind:
a) Community
opening
Bush clearing,
and pits
(foundations)
supply

of stones,

Organization

access

gravel,

of community

b) CD Department

roads

sand,

- excavating

wood and other

& backfilling
material

work

/ SATA-Helvetas

Survey, projecting
& planning
Administration
and supervision
Total
cost

cost

of the project

per capita

5. Proposed

/ actual

(= cash + kind)
& stage

financing
10 %
10 %

Village
contribution
in Cash
Village
contribution
in kind
Government contribution
in cash
(various
grants)
CD / SATA-Helvetas
in kind
Foreign aid in cash

20 %
20 %
40 %
100 %
154

available

of trenches
locally

6. Organization
The Project
organizes
organizes
collects
prepares

the project

Committee:
meetings & community work
the supply of local material
the village
cash contribution
applications
for grants
(government

Consultants

to the Committee:

- the community development
to the Conslittee

7. Maintenance

officer

and the engineer

remark

These remarks
project.

are meant to recommend in a summary the construction

to the technical

Map of the country
Plans of the village
to be constructed.
Hydraulic

points
to consider
before planning
Chapter 6 where all important

and recommendation

The completed report
will
be signed
by the CD-Officer
of the area.
Annexes

are consultants

of the project

Maintenance
is one of the most important
a water scheme. Please read with attention
information
is given.

8. Final

& other)

profile

by the engineer

of the

(or technician)

report

indicating
(lay-out)
of a water

the situation
including
supply.

155

of the village.
all

buildings

and installations

and

5-2

EXECUTION OF PROJECT

5-2.1

BEFORE STARTING A PROJECT

A project
should not start
before it is approved
Department and by the local authorities.

by the Community

Development

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

to
to
to
to

5-2.2

have
have
have
have

also:

recruited
all masons & labourers
needed
all tools,
material
& machines ready
completed the technica,4L report
with execution
prepared the list
of m,'iterial
to be ordered

DURING THE CONSTRUCTION

Close supervision
of a construction

is necessary
project.

At the project
site,
daily
book must be kept regularly

plans

!
to build

properly

the different

elements

reports
must be made and a iog book with
by the foreman.

material

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
d report
and a financial
statement
are required
in order
amounts (Progress Report).

5-3

COMPLETEDPROJECT

5-3.1

FINANCIAL STATEMENT

of the construction,
to receive
further

As soon as the project
has been completed a financial
statement
handed over to the department
concerned
(Community Development
departments).

will
be
or other

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 REPORTAND HANDING-OVER FILE

A final
report of the completed
time as the financial
statement
Committee.

project
will
be handed over at the same
to the CD department
and to the Project

The final

the

report

should

Technical

A brief

Comments on the technical
aspects
(possibility
of extension,
lifetime
special
care) and on the expected
expectation
of installations,
output,
influence
of the new construction
an the villagers
and their
surroundings.

Handing over note concerning
the buildings
& installations
-Committee and a duty sheet to the caretaker. -

history

technical

following:

5-3.3

report,

isnclude

details

& plans

of all

constructions.

of the project.

to the

Project

DRAWINGOF 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
etc.)
and houses of the village
with foot path.
valves,
cleaning
valves,

5-3.4

DOCUMENTFILE OF A COMPLETEDPROJECT

Technical
report,
other engines).
Correspondence

estimates,
and receipts

Minutes

of meetings

Repairs,

possibilities

Final
All

report
situation

with

calculations,
of material.

and opening

addresses.

of extension.
financial

and execution

statement.
plans.

instructions

(pumps, turbines

Chapter

Table

MAINTENANCE OF RURAL WATER SUPPLIES

of contents

page

6-l

MAINTENANCE GENERAL

161

6-2

MAINTENANCE-INSTRUCTIONS

161
161

2.1

Maintenance

of wells

2.2

Maintenance
of catchments
6-2.2.1
Maintenance
of spring catchments
6-2.2.2
Maintenance
of barrages and river

162
intakes

2.3

Maintenance
of treatment
stations
6-2.3.1
Maintenance
of sedimentation
tanks
6-2.3.2
Maintenance
of slow sand filters

163

2.4

Maintenance

of storage

164

6 - 2.5

Maintenance

of water

2.6

Maintenance

of distribution

6 - 2.7

Maintenance

of pumping

tanks

165

points
system
stations

159

165
165

MAINTENANCE GENERAL

6-1

Once a water scheme is completed it is necessary
to pay great attention
its maintenance
so as to ensure a continuous
supply of drinking
water
good quality
and sufficient
quantity.

to
of

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 WATERNO LIFE :
Organization

of the maintenance:

Before the completed project
is handed over to the villagers
of the water supply should be organized
taking
the following
consideration:

the maintenance
points
into

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
of the project
as it is described
in the following
chapters.

The engineer
handing over

All financial
maintenance

concerned is responsible
the project.

to instruct

the caretaker

matters and distribution
of responsibilities
should be regulated
in advance.

6-2

MAINTENANCE-INSTRUCTIONS

6-2.1

MAINTEN.ANCEOF WELLS

maintenance

for

before
an efficient

Every week:
Control
the cleanliness
of the well,
hand pump and surroundings.
If necessary
by the population.
The drainage
arrange for cleaning
work, to be carriedout
of waste water (overflow)
is very important,
to prevent
any contamination
of
the ground water.
Every

month:

Grease or lubricate
pump, follow
strictly
maintenance.
Every

four

every hand pump (compare Fig. 85). With an engine-driven
the manufacterer's
instructions
regarding
service
and

months:

Check the construction
should be done without

and buildings
and repair
all damages.
delay as soon as they are disccvered.

Minor

repairs

All necessary maintenance
work should
contact
cannot be solved by yourself,
Office,
which will
give the necessary
community and local council
concerned.

6-2.2

MAINTENANCE OF CATCHMENTS

6-2.2.1

Maintenance

Protective

of spring

be done regularly.
If any problem
the nearest Community Development
assistance
in cooperation
with the

catchments

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.
people concerned to
Prevent any farming inside
the catchment area, report
Special attention
must be
the local authority
or to the administration.
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
Water measurements should be taken whenever
the grass must be kept short.
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
soon as they are discovered.

of the engineer

have to be reported

Comments:
All necessary maintenance
work should be done regularly.
If any problem
contact
the nearest Community Development
cannot be solved by yourself,
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
If unusual contamination
is observed find its cause (farming,
latrines
etc.)
fertilizer,
washing,
fishponds,

162

quality.

Monthly:

Minor

inspect
the overflow,
damage.

check if

there

are any cracks

or other

repairs:

Minor repairs,
delay.
Major

once a fault

is discovered,

have to be done without

any

repairs:

Repairs which require
the attention
of the engineer
have to be reported
as
to prevent waste of water,
contamination
and
soon as they are discovered,
further
damage.

6-2.3

MAINTENANCE OF TREATMENT STATIONS

6-2.3.1

Maintenance

of sedimentation

tanks

Inspections:
clean and drain the tank. Keep installations,
holes and drains clean. Cut the grass arount
Grease doors, locks,
valves etc.

Monthly:

Twice a year:

general check up of the buildings
leakages.

for

overflow,
vent
the entrances.

damages such as cracks

or
Minor

repairs:

Minor repairs,
once a fault
is discovered,
to prevent waste of water and contamination.
Major

have to be done without

any delay

repairs:

Repairs which require
the attention
of the engineer
have to be reported
as
to prevent waste of water,
contamination
and
soon as they are discovered,
further
damage.

6-2.3.2

Maintenance

Cleaning

of slow

sand filters_

of the filter:

the water has to be drained
first.
Then 1 cm
If a filter
requires
cleaning,
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
This process is repeated
until
the minimum thickness
for
from the surface.
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 contamiand rub
nation is washed out. To check if the sand is clean , take a hand-full
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
mhould be followed
strictly.
by the engineer
for each project

instructions

given

Engineers
in Cameroon are presently
testing
special
sand wash places.
results
are available,
a standard
design could be worked out.
General

Once the

inspection:

Twice a month:

Inspect the filter
plant,
keep installations,
overflows
drains clean.
Cut the grass around the entrance.

Twice a year:

General

check

up of buildings

once a fault
is discovered,
Minor repairs,
to prevent waste of water or contamination,

for

damages (cracks

have to be done without

and

or leakages).
any delay

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 STORAGETANKS

Inspections:
Monthly:

Clear the surroundings.
Keep vents,
drains,
water quality
and for possible
contamination.
(valves),
look for leaks.

Twice a year:

look
Clean the storage-tank,
cracks,
leakages,
plastering,

Minor

for damages on the buildings,
installation.

repairs:

Once a fault
is discovered,
repairs
waste of water or contamination.
Major

etc. clean. Check the
Check installation

have to be done without

delay

to prevent

repairs:

Repairs which require
the attention
of the engineer
have to be reported
soon as a fault
is discovered,
to prevent waste of water, contamination
further
damage.

164

as
and

6-2.5

MAINTENANCE OF WATER POINTS
. _---

Maintenance

of the spring

catchment:

clean

Monthly:

clear the surroundings,
cut grass. Keep air vents,
drain,
etc.
clean, check quality
of water and for possible
contamination.
twice

Important:

a year:

Greatest

6-3.1

Weekly;

At least

wash-basin,

see chapter

any

clean the storage-chamber,
as cracks.
attention

must be given

Minor repairs,
once a fault
is discovered,
to prevent waste of water or contamination.

6-2.6

look

damages such

to the drainage.
have to be done without

any delay

MAINTENANCE OF DISTRIBUTION SYSTEM

Stand pipes,

wash places

Daily:

Cleaning
pipe.

Weekly:

General

Monthly:

and shower houses:

by the consumer.
check

Special

up and special

Valve

care should

be given

to the drain

to avoid

loss

cleaning.

Cut the grass if necessary.
Leaking taps have to be repaired

Soakaways don't need much maintenance.
have to be cleaned immediately.

immediately
In case they

are blocked

of water.

by dirt

they

chambers:

Twice a year: Inspect
and clean them. Any broken slab
Repairs have to be done without
delay once a fault
is
should be closed and opened during these inspections.

6-2.7

for

should be replaced.
discovered.
All valves

MAINTENANCE OF PUMPING STATIONS

Pump and drive:
The manufacturer's
A special
instruction
can be made available

maintenance

instructions

have to be strictly

manual for each pumping station
(from the appropriate
engineer).

regarding

followed.
maintenance

Buildings:

Monthly:

Check installation
for correct
functioning
Look for leakages.
Paint the installation,
that overflows
and drains are clear.

(valves or stopcocks).
grease locks,
etc. Check

Chapter

SELECTED BIBLIOGRAPHY

- Hand Dug Wells and Their
1977, ISBN 0.903031.27.2

Construction
(f 3.95)

- Hand Pump Maintenance
in the Context
Pacey, A., 1977, ISBN 0.903031.44.2

- Water for the Thousand Millions,
ISBN 0.08.021805.9
(f 2.50)

- Water Treatment
(f 2.00)

- Water, Wastes and Health
1977, ISBN 0.471.99.4103

by Watt,

of Community
(E 1.25)

by Pacey,

and Sanitation

S. and Wood, W-E.,

A.,

by Mann, H.T.,

in Hot Climates
(f 10.75)

Note: All titles
above from: Intermediate
9 King Street,
London WC2E EHN, U.K.

Well

Projects.

1977,

1976,

ISBN 0.903031.23X

by Feachem,

Technology

R.,

et al.,

Publications

Ltd.,

- Slow Sand Filtration
Countries
by Dijk,

- Hand Pumps by McJunkin,

E.F.,

Technical

- Water Supply for Rural Areas
1959, Monograph No. 42

and Small

- Typical
Designs for Engineering
Components in Rural Water Supply,
published
by WHORegional Publication
South East Asia Series,
World
Health House, Indrapratha
Estate,
Ring Road, New Dehli 110 002, India

for Community Water Supply in Developing
J.C. van, Technical
Paper No. 11, 1978 (US$ 10)
Paper No. 10, 1977 (US$ 10)
Communities

by Wagner & Lanoix,

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
(approx.
US$ 18)

11.

- Small

Water Supplies

Note: Both titles
Mauritskade
bla,
12.

- Handpumps for
(US$ 1.95)

13.

- Using

Digging

in Tanzania,

1978,

US$ 4.50)

from: TOOL Foundation,
Communications
1092 AD, Amsterdam, The Netherlands

Collective,

Village

from:
Ave.,

by Ross Institute,

Project

1978 (approx.

Water Ressources,

Note: Both titles
3706 Rhode Island

of a Well

Wells

by Spangler,

VITA 1977,

C.D.,

VITA 1975, No. 28,

No. 38 (US$ 5.50)

VITA, Volunteers
in Technical
Mt. Rainier,
Maryland 20822,

167

Assistance,
U.S.A.

14.

- Water and Waste Water Disposal,
1968, Wiley, New York

15.

- Rural Water Supply
New York

16.

- Taschenbuch der Wasserversorgung
Stuttgart,
Germany

and Sanitation

All titles
may also be ordered
CH-9000 St. Gall, Switzerland

through:

168

Volume II,

by Wright,

by Fair

F.B.,

& Geyer,

1977,

Krieger,

by Mutschmann-Stimmelmayr,

SCAT, Varnbiielstrasse

14,

1973,

Chapter

INDEX OF KEY WORDS

Administration
,Aggressivity
Air

prevention

115

of...

of water

Anchoring

of pipe

Asbestos cement
aggressivity
friction
loss
pressure
test
prevention
of

of water

pockets,

Analysis

151

of projects

Back-filling

127

line

106
24
112
130
27

pipes
towards AC-pipes
in AC-pipes
of AC-pipes
corrosion

of trenches

Bacteriological

field

Bacteriological

standards

124

test
for

drinking

167

Bibliography

Calculation

of piping

Carbon dioxide

110

(CO2)

Cement products
aggressivity
towards cement products
prevention
of corrosion
I

80, 162

Barrage

water

Centrifugal

analysis

Chemical

standards

of water
for.drinking

41
water

of water

Climatic

pattern

Coffee

washplace

Coliform

of water

Chemical

Chlorination

143

pumps

Characteristics

24
26

bacterial

20
20
6
137

count

19, 40

Completed project

156

Connection

134

details

Consumption of water
peak eonmumption.
specific
consumption
Corrosion,

prevention

111

34
26

of...
169

Daily

water

Deep well

consumption

pump

141

Degree of hardness
Distribution

buildings

135

Distribution
system
type of distribution
systems
design of the distribution
system
maintenance of the...

103
103

110
165

Drainage

in Cameroon

Drinking

water

standards

Execution

of project

Field

test

Field

work

156

Filtration
Final

90,

report

157

Flow measurement
Fountain,

public...

136

110
112 - 114

Friction
loss in pipes
. ..diagrams
0

Galvanized steel pipes
friction
loss in galvanized
prevention
of corrosion
Gravity,

steel

Hand pumps

calculation

cycle

Intakes

110
3
5

Infiltration
Inspection

of piping

150

Hydr0 pump
'I

112

148

ram

Hydrology
hydrologic

17
50

Head loss in pipes
Hydraulic

107
114
28

140

Hardness of water
Hydraulical

pipes

supply by...

Ground water
supply of ground water
H

chamber

73
82
12

114

K
L

Laying of pipes

123

Lay-out of water supplies
lay-out in stages
lay-out of distribution

49
50
103, 51

Location
M

of water

Maintenance

system

sources

of rural

water

supplies

159
125

Marking of pipeline
Measuring

of water quantities

MPN Index

(coliform)

test

. ..field
N

Organization
. ..of maintenance
. ..of project
Outlet

161
155
76, 89

building

111

Peak consumption

PH - value
Pipes
pipe connections
piping material
laying of pipes

to buildings

Plastic pipes
friction
loss in plastic
prevention
of corrosion
Plunger

pump

Pressure

test

Pressure

zones

Project

pipes

134
105
123
106
113
29
139
130

of the pipeline

104
151

administration

Pumps, types of pumps
maintenance of pumping stations
pump drives
of water
measurements
,..of spring water

139
165
144

Quantities

35
65

171

Rainfall
intensity
of rainfall
quantity
of rainfall
tables of monthly rainfall

6
12
6
11

Rain water storage

Rectangular

weir

River intake

Run-off

Sedimentation

83, 163

Service

life

Shower house, public...

138

Slow sand filter

90, 163

Specific

consumption

Spring
location of spring
spring catchment

17, 65
35, 49, 66
67, 162

Stages,

design

in stages

Standards

for drinking

Standbipe
. ..with

wash table

water

19
135
137

Steelpipes
Storage,

107
storagetank

99, 164

Stream
. . . catchment
t

Technical
Testing

18, 49
80, 162

report

153

the pipe line

130

Thompson weir

Thrust-blocks

127

Treatment of water
lay-out of treatment station:
maintenance of treatment station

83
97
163

Trenching

120

Vacuum, prevention

of...

118

Vt31&3
valve chambers

108, 118
132
172

136
137

Washplace, public...
Coffee washplace
Water
aggressivity
of water
analysis
of water
characteristics
of water
ground water
standards
for drinking
water

22
40
15
17
19

Water lifting

139

Water point

78,

Water sources
location
of water

source

Water treatment
Wells
handpumps for wells
maintenance
of wells

17
35
83
55
140
161

165

Appendix:

NORMPLANS AND SCHEMEPLANS

Norm plan No.

Title

of plan

Public

stand pipe

Public

wash place

(in concrete

Public

wash place

(in masonry construction)

Public:fountain
Interruption
Water point

construction)

(in masonry construction)
chamber with

ball

valve

(in masonry construction)

Scheme plan No.
7

Plumbing scheme of single

storage

tank

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
LIST OF MATERIALS
STAND
EISNT

SOAKAWAY
CEYE”T 1 N&o
STD”ES IOIn’

PIPE
5 8165

WCLDCD WESN 26 I 46c.m
RODS
0 6mm SOm
Pm
@ lmrn

YND
oN~y-Q----JDN

2rm.

6mm

?m.

’

t2p-J.
16

0 cmm

6mm

Ollm’

= 1.45m

1.2om

AC
50
4Om
1 PIECE
G.I. 4’
0.25m
1 PIECE. TAP 4’ 1
6.1. SOUKET Y 1.
0.I. ELEW u
STOKf5
5m’
SANII
lm’
eMoN
BLOCKS 6~ 16 a 20s4Dom

: lm77m
10
3 I 1.5Dm

130
=

OJOrn

4’or v
1 *’ nr I’
-------T

51 SLOPE

r
L-J
L-

z .-.

&!!
1

IS
I
---5

- ---~---~~-~---~
SECTION B-B

SECTION A- A

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
50cm WITH S0cKfT
1 PIECE
G.I. 2’ 3Ocm TNREAOED ONE EN0 1 PIfCL
TAP w 1 *I?? e
SCCKETC I # , ”
ELKlwtl
, 1,
WELDED MESH 1”s 210 I 0.70m’
Zno 195 I 0.75 In’
1 no 0.35 .s 0.25 m*
AC 100 4m
RODS lo-.
I em ,,&
. O.,sn

-3.1.
2’

“

Tn..

,6nn

SOAKAWAV
CWNT - 15 l&S
SAN0
- id

Y”

166

10
, . IWIn

R005;

#‘mm

141

j2D’

20000

360

/2D!lDj

!2G!

,;,‘,

SECTION A-A

SECT&

B- Ei

I
W",W.JAY

SECTIOiJ C-C

LIST OF MATERIALS

I
-

::
N

200

mxoE0
A.c.100
5mrvlr
5GND

WLIll mN 5LM5
4m
1011'
414

SOAUAWAV
CEnaY
a05

4ilhc5
~~54Nl

l A9

WELaD
5rom
YIQ

YW roll
12d
1Rl'

&?w

LlITMNOE

SUI

451 lW*m
ORAIM PIPE

Ii ’
!4

’

”

- hl

’

I t/!-l

-0m

uA5ONRY

LEAN CONCRE:TE

130

30
1

‘I

SECTION A A

LIST OF MATERIALS
FOUNTAIN
370

CEMENT
15 BAGS
G.I. PIPES Y 3Ocm 9 PIECES
G.I. SOCKETS +t’
4
y
Y’
4
I
iAPs
w
a’$2
”
G.I. TEES
**
Y&1
y
G. I. TEE
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

, 30

SOAKAWAY
CEMENT
ROOS

‘9

‘g

140

14no 0 6mm

10
c

WELDED MESH EOR ENTRANCE
STONES
SAN0
r.PAVFI

PAVED

160cm.

10
-) =

170
SLAB

45x

190cm

105 cm

I.[10 , -91

7
-

12 ml
1 m’
n*?“l

FLOOR

110

4 BAGS
0 6mm 54m
17no $6mm

L 30

310

L
1

t.llNlsTRY OF A4mcuLIuRE
CC6iNNNlTy DEVELOPMENT DEPARMENT
. LWREO REPUBLIC OF CAMERa
HElMETAS
SWtS6 ASS4YJATION FOR TEcHNlw
ASSISTANCE ( 5ATA 1

MANUAL FOR RURAL MITER SLWLY

PUBLIC FOUNTAIN
IN MASONRY CONSTRUCTION

PLAN

KEY:
EEZZZl CEMENT BLOCKSOR
STONE MASONRY
EZZil

CAST CONCRETEOR
STONE MASONRY

lSZZZ?Y REINFORCEDCONCRETE

(a) D ACCORDING TO THE MEASJJREMENTS
OF THE BALL VALVE
OVERFLOW

AND CLEANING

PIPE

SECTION B - B

SECTION A -A

Cl = CLIMBING

IRONS

BALL VALVE

ISOMETRIC VIEW OF MANHOLE

VIEW C-C

J
COMMUNITY DEVELOPMENT DEPARTMENT
UNITED REPUBLIC OF CAMEROON

MINISTRY OF AGRICULTURE

I/ I

DRAIN PIPE
I

HELVETAS
SWISS ASSOCIATIONFOR TECHNICAL ASSISTANCE ( SATA)
“.
_”

,_
_I_
‘,

,’
,,

-./
),

GROUND PLAN

MANUAL FOR RURAL WATER SUPPLY

INTERRUPTIONCHAMBER

.( ‘,:..’ WITH BALL VALVE
.‘b~..‘;‘,,..
,,’
:,’ ._I) (.f,.‘
<‘,.
I~
i2;I._,;,
;, -, ’i‘
.-?,...’
‘,
,,‘(,‘.
.,:

DRAWN:
BH
DATE : MAY 1980

NORM PLAN
No. 5

STORAGE VOLUME :
ACCORRINGTO THE YIELD OF THE SPRING
DURING DRY SEASON AND TO THE DAILY
CONSUMPTION

RETAINING WALLS
TO THE TERRAIN

ACtOR

KEY :
-

STONE MASONRY
CAST CONCRETE

SECTION

B -B

REINFORCED CONCRETE

ISOMETRIC VIEW

SECTION

StLIIUN

C-C

A -A

SECTION D- D

SToRAGE :IEANING

I
.,

YYI.1,.
-4uNlTY
DEVELOPMENT DEPARTMENT
:n Dcc4im tm -- -. . .-m--m.

UNITL,

&:;Q.:, ,;. I
‘)_
J,.i
:,,.
c.,,,._, ‘‘,’
,r
*,>..”
C’.~s,.

l-h1 QJPLIL

LAMkKUUN

MINISTRY OF AGRICULTURE

1
,?%

HELVETAS
_,.,I _^ -mm--. -->WI>S ASSLKIATION FOR TECHNICAL ASSISTANCE ( SATA)

MANUAL FOR RURAL WATER SUPPLY

& . .;,)WATERPOINT

-.I:‘.’
:,I_i
,. I.’ / IN MASONRY CONSTRUCTION

ORAWN :
DATE : MAY 1::

NORM PLAN

PIPE

DRAIN PIPE OR
DRAIN CHANNEL

GROUND PLAN

T’T-

AERATION WITH
PROTECTIVE COVER

BALL VALVE
.-__

b AERATION DISTRIBUTION
--w
--

TAP
7
>

GATE VALVE

OVERFLOW ~

i+r

SUPPLY FROM
CATCHMENT (FILTER )
DISTRIBUTION
STRAINER
[ KUGLER 619111
-

COMMUNITY DEVELOPMENT DEPARTMENT
UNITED REPUBLIC OF CAMEROON
:.~

OVERFLOW PIECE
[ KUGLER 61642 1
AND CLEANINGPIPE

MINISTRY OF AGRICULTURE

HELVETAS
SW&S ASSOCIATION FOR TECHNICALASSISTANCE (SATA 1
DRAWN BY BTC
DATE : MAY 1900

PLUMBING SCHEME
SINGLE STORAGE TANK

AERATION WITH
PROTECTIVE COVER

BALL VALVE

BALL VALVE
r

AERATION DISTRIBUTION

TAP

OVERFLOW

GATE VALVE

OVERFLOW

i
I

STRAINER
[KUGLER 61911I

STRAINER
[KUGLER 61911 I-- @
DISTRIBUTION
TO VILLAGE
-;
I-

L
-

CC%ll’dJNlTY
COMl’dJNlTY DEVELOPMENT DEPARTMENT
UNITED REf’UBUC OF CAMEROON

,;
!,

HELVETAS
SWISS ASSOCIATIONFOR TECtiNlCAL ASSISTANCE (SATA 1

;;,::
,; I
.,_
I\:
::
2..

I.$ ’
l:;

I.i
;,._,
i..,:
b’j.
:
&IL:
,p:>
2:,
-,;,;
;f,;; ;

OVERFLOW PIECE
IKUGLER 616421

GATE VALVES

MINISTRY OF AGRICULTURE

MANUAL FOR RURAL WATER SUPPLY

PLUMBING SCHEME OF
DOUBLE STORAGETANK

DRAWN BY BTC
DATE : MAY 1960

SCHEME PLAN
No. 0

SUPPLY FROM
CATCHMENT(FILTER1

PLUMBING SCHEME
DOUBLE STORAGE TANK

COMMUNITY
TECHNICAL

MANKAHA
WATER

DEVELOPMENT
SERVICE

DEPARTMENT
BAMENDA

BAFUT
DRAWN:

DATE

: 10:03:?5

HODiFYD:O.NC
HYDRAULIC

MUM

NEKURU

SEAT PUBLICATIONS

Publ.
No.

Jean-Max Baumer: Schweizerische
Kontaktstelle
fur Angepasste
gratis
Technologie
(SEAT), St. Gallen 1977, 39 Seiten,

Jean-Max Baumer: Angepasste Technologien
fiir Entwicklungslgnder,
Literaturstudie,
St. Gallen 1977, 132 Seiten
(out of print)

Jean-Max Baumer: Angepasste Technologien
fiir Entwicklungsldnder,
Bibliographie,
St. Gallen 1977, 307 Seiten
(out of print)

Jiirg

Sabine Huber: Probleme des Technologie-Transfers
13ndern in EntwicklungslBnder,
St. Gallen
43 Seiten
(out of print)

Gerhard Schwarz:
des Konzepts
Cindern,
St.

Otto

Helvetas:
Manual for Rural Water Supply,
St. Gall 1980, 175 pages,
with many detailed
constructional
scale-drawings,
SFr. 34.-(US$ 20.--j

Nipkow: Angepasste Technologien
fur EntwicklungslZnder,
Sonnenenergie-Gerate
fur Haushalte,
St. Gallen 1977,
62 Seiten,
Fr. 8.50

Langenegger:
in Aethiopien,

von Industrie1978,

Hemmnisse und Hindernisse
bei der Verwirklichung
der Angepassten Technologie
in EntwicklungsGallen 1978, 53 Seiten,
Fr. 14.-Einsatz
von Bohrmaschinen
fiir die Wasserbeschaffung
St. Gallen 1979, 43 Seiten,
Fr. 14.--

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