WATER DISTRIBUTION SYSTEM

WATER SUPPLY
AND
WASTEWATER
ENGINEERING

TOPIC 4:

WATER SUPPLY DISTRIBUTION SYSTEM

INTRODUCTION

Water Distribution Systems
• The purpose of distribution system is to deliver water to

consumer with appropriate quality, quantity and
pressure. Distribution system is used to describe
collectively the facilities used to supply water from its
source to the point of usage.

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REQUIREMENTS OF GOOD
DISTRIBUTION SYSTEM

• Water quality should not get deteriorated in the distribution
pipes.

• It should be capable of supplying water at all the intended
places with sufficient pressure head.

• It should be capable of supplying the requisite amount of
water during fire fighting.

• The layout should be such that no consumer would be
without water supply, during the repair of any section of the
system.

• All the distribution pipes should be preferably laid one metre
away or above the sewer lines.

• It should be fairly water-tight as to keep losses due to
leakage to the minimum.

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Water Distribution System

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WATER DISTRIBUTION
SYSTEM

• A water supply distribution system may be
classified into three typical types:

• i. gravity system,
• ii. pumped system, and
• iii. combined gravity and pumped system.

• The choice of type of distribution system
depends on the topography, location and
extent of the distribution area, elevation and
site conditions.

• Where adequate elevation of the supply is
available and other site conditions permit, the
gravity system shall be the most preferred type
of distribution. Where the gravity type of system
is not feasible, the gravity and pumped
combination shall then be considered. The
gravity and pumped combination system is the
most commonly used system. The direct
pumped system is least preferred and may only
be used in large systems.

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ADVANTAGES AND DISADVANTAGES
OF THE TYPES OF DISTRIBUTION
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System Advantages

1. Gravity - Most reliable

2. Pumped and - Low operational costs - Problems associated
Gravity - Least cost option with operation and
Combination maintenance of
under certain pumping systems.
topographical
conditions.

3. Direct pumped - Pressure and flow can - Problems associated

be easily regulated with operation and

- Remedial action can be maintenance of

speedily taken pumping systems.

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Components in Water Distribution System

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SELECTION OF TYPE OF
PIPE MATERIAL

The major factors to be considered when selecting the
type of pipe are :
• Working and test pressures, including surge pressure
• Strength of pipe to withstand designed internal and
external loads
• Durability of the pipe
• Suitability and workability for laying and operating
requirements
• Capital, operation and maintenance costs.
• Extent of possible leakage

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ADVANTAGES AND DISADVANTAGES OF VARIOUS PIPE
MATERIALS

Pipe materials Advantages Disadvantages

Cast Iron - Good corrosion resistance - Weak to impact
Ductile Iron - Many types of joint available - Heavy
-Fairly good corrosion resistance
- Strong to impact - Heavy
- High cost
Asbestos Cement - Low cost - Relatively low flexural strength –
- Free from electrolysis
- Relatively lightweight high no. of breakages.
- Easy to cut, fit & handle - Easily punctured by excavating
- Easily drilled and tapped
equipment
Steel - Strong in tension & bending - Quite easily damaged due to
- Strong to impact
- Longer length, thereby less mishandling
- Comparatively, A.C. pipelines
chances of leakage
have more joints thereby
increasing chances of leakage.
- Weak to electric corrosion
- Extensive time taken for welding

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ADVANTAGES AND DISADVANTAGES OF VARIOUS PIPE

MATERIALS

High Density -High flexibility - difficult to joint – requires a
Polyeththylene -Lightweight special heating equipment for
- very good corrosion resistance joint.
-strong to impact
- available in coils (for outside - high cost ( for greater than 200
mm )
diameter less than 180mm )
-low internal friction -Require adaptors for connections
to fittings and other pipe
materials.

- degraded by ultra violet

-lightweight radiation, hence storage

Unplasticised polyvinyl -very good corrosion resistance problems

Chloride -flexible -easily punctured

- low internal friction -quite expensive and fluctuates

with world petroleum prices

-easily damage by impact –careful

handling required

Glass fibre reinforced -lightweight -not suitable for high pressure
plastic - good corrosion resistance pipelines because of relatively
-low internal friction interior strength

-deform easily – leakage from joint

can be high

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LAYOUTS OF
DISTRIBUTION NETWORK

• The distribution pipes are generally laid below the road
pavements, and as such their layouts generally follow
the layouts of roads. There are, in general, four different
types of pipe networks; any one of which either singly or
in combinations, can be used for a particular place.
They are:

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DEAD END SYSTEM

• It is suitable for old towns
and cities having no
definite pattern of roads.

Advantages:
• Relatively cheap.
• Determination of

discharges and pressure
easier due to less number
of valves.
Disadvantages
• Due to many dead ends,
stagnation of water
occurs in pipes.

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GRID IRON SYSTEM

• It is suitable for cities with
rectangular layout, where the
water mains and branches are
laid in rectangles.

• Advantages:
• Water is kept in good

circulation due to the absence
of dead ends.
• In the cases of a breakdown in
some section, water is
available from some other
direction.
• Disadvantages
• Exact calculation of sizes of
pipes is not possible due to
provision of valves on all
branches.

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4.2 Water Storage

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STORAGE TANKS

One of the most integral parts of the distribution system is the storage facility. Storage tanks are
used as a means of providing head for a water distribution system. During periods of low
consumption, water is pumped to elevated tanks. During periods of high consumption, the stored
water is drawn upon to augment pumped water, allowing fairly uniform rates of pumping and
mitigating diurnal variations. Storage tanks also provide excess capacity for fire protection.
Distribution reservoirs, also called service reservoirs, are the storage reservoirs, which store the
treated water for supplying water during emergencies (such as during fires, repairs, etc.) and also
to help in absorbing the hourly fluctuations in the normal water demand.

The main functions of a reservoir/storage tank can be listed as follows :-
(a) To provide a reserve of treated water in order to minimize interruptions of supply due to

breakdowns
(b) To provide a reserve to meet a fluctuating demand
(c) To act as a break pressure tank where the range of elevation of an area serve makes it necessary

to sub-divided the distribution system into zones, and
(d) To provide a reserve of water for fire fighting. The amount of contingency storage to be

provided determines the size of the reservoir

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TYPES OF RESERVOIRS/STORAGE
TANKS

1. Underground reservoirs.
2. Small ground level reservoirs.
3. Large ground level reservoirs.
4. Overhead tanks. – elevated tanks

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STORAGE TANKS

General

• The main functions of a reservoir can be listed as follows :-
• To provide a reserve of treated water in order to minimize interruptions of
supply due to breakdowns
• To provide a reserve to meet a fluctuating demand
• To act as a break pressure tank where the range of elevation of an area served
makes it necessary to sub-divided the distribution system into zones, and
• To provide a reserve of water for fire fighting. The amount of contingency
storage to be provided determines the size of the reservoir

• In a water distribution system, reservoirs are functionally divided into 2 categories,
i.e.
• Balancing reservoirs and
• Service reservoirs

• Both types of reservoirs must be structurally safe and watertight.

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TYPES OF RESERVOIRS
AND STORAGE TANKS

• The types of reservoirs and storage tanks include :-

• Reinforced concrete
• Pre stressed concrete
• Galvanized pressed steel
• Fiberglass reinforced polyester
• Steel fused with glass

• In selecting the types of reservoirs for a distribution
system, consideration should be given to the various
factors such as capital cost, cost of maintenance,
topography and life expectancy.

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TANK CATEGORIES

In a water distribution system, reservoirs
are functionally divided into 2 categories :
(a) Balancing reservoirs and
(b) Service reservoirs
Both types of reservoirs must be
structurally safe and watertight.

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BALANCING AND
SERVICE TANK

✓ Generally, the main function of balancing reservoirs is to receive pumped
treated water and to distribute it substantially to a or several service
reservoir/s.

✓ Balancing reservoirs are normally built near treatment plants. When there
is a draw-off from any of the service reservoirs, water will flow from the
balancing reservoir in the distribution system, the required flow rate into
the service reservoir can be maintained due to the constant supply head
between the two reservoirs. Sizing of the balancing reservoir should be
based on the storage required to balance the inflows and outflows.
Generally, the capacity of the reservoir should be equivalent to two hours
of the inflow subject to a minimum capacity of 450 m3 and a maximum
capacity of 9000 m3.

✓ Service reservoirs supply substantially to reticulation systems.

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STORAGE CAPACITY OF DISTRIBUTION
RESERVOIRS

The total storage capacity of a distribution reservoir is the summation of:
1. Balancing Storage: The quantity of water required to be stored in the

reservoir for equalising or balancing fluctuating demand against constant
supply is known as the balancing storage (or equalising or operating storage).
The balance storage can be worked out by mass curve method.
2. Breakdown Storage: The breakdown storage or often called emergency
storage is the storage preserved in order to tide over the emergencies posed
by the failure of pumps, electricity, or any of the mechanism driving the
pumps. A value of about 25% of the total storage capacity of reservoirs, or 1.5
to 2 times of the average hourly supply, may be considered as enough
provision for accounting this storage.

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3. Fire Storage: The third component of the total reservoir storage is the fire
storage. This provision takes care of the requirements of water for extinguishing
fires. A provision of 1 to 4 per person per day is sufficient to meet the
requirement.
The total reservoir storage can finally be worked out by adding all the three
storages.

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VALVE

A WIDE RANGE OF VALVES ARE AVAILABLE TO
STOP, ISOLATE, START OR

REGULATE WATER FLOW IN A WATER DISTRIBUTION
SYSTEM.

Scour Valves Sluice Valves
• Sluices valves are used -used to stop the flow of water and

as scour valves. to isolated a section of the water
• Shall be installed at the main
- it consist of flanged sluice valves
low points and at points and plain-ended valves
where scouring may be - all sluice valves shall be of the non-
required, so as to drain rising stem and cap type and
sediments from the clockwise closing
pipeline. - The normally recommended interval
for the spacing of the sluice valves
Butterfly Valves shall be 1.5 km on most
• Not designed to be leak transmission and distribution
pipelines. However, the interval
tight but mainly used for can be increased to 3 km on
flow regulation in the pumping lines. At junction, the
water system distribution number of sluice valves shall be
such that it allows flexibility and
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- sluice valves shall always be placed
downstream of scour chamber.

Air valves VALVE
• Two types of air valves are used,
Reflux valves
namely the single orifice and • Also known as non-return valves
double orifice air valve.
• Single orifice air valve used as to or check valves that can
discharge air which may proceed flow in one direction
accumulate in sections of only.
pipeline under working • In water distribution system, reflux
conditions. valves shall be used at rapid but
• Double orifice air valve is of the non-slam closure under high
combined small and large orifice velocities and surge conditions.
pattern which serves to discharge
air during the filling of the pipeline Ball or Float Valves
and to admit air while the • -normally used at the end of the
pipelines are emptied.
• Both types of air valves shall be inlet pipe to a suction tank or
designed for operation at a reservoir when flow into the
maximum permissible working reservoir or tank is by gravity.
pressure of 16 bar. • -The function is to allow water to
• Transmission, distribution and flow until a predetermined level is
reticulation pipelines shall have reached.
air valves.
• A general rule is that the air
valves shall be positioned at
intervals not greater than 1 km
apart.

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VALVE

Altitude Valves

• Used to control the
level of water in
elevated reservoirs

• Shall be installed in
chambers and shall
be provided with a
bypass pipe
arrangement so that
distrubption to that
supply of water is
minimized when the
valve is being
maintained.

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4.3 Non-Revenue Water ( NRW)

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Non-Returned Water (NRW) N

Non revenue water (NRW) is water that has been produced and is lost before it reaches the customer.
Losses can be real losses (through leaks, sometimes also referred to as physical losses) or apparent
losses (for example through theft or metering inaccuracies). High levels of NRW are detrimental to
the financial viability of water utilities, as well to the quality of water itself. NRW is typically
measured as the volume of water "lost" as a share of net water produced. However, it is sometimes
also expressed as the volume of water lost per km of water distribution network per day.

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THE COMPONENTS OF NRW

Commercial losses (Apparent losses) such as meter under-registration,
illegal use including fraudulent and unregistered connections and legal
but usually unmetered uses like firefighting, flushing of mains, street
cleaning, etc.
Physical losses (real losses) such as pipe breaks and leaks,
storage reservoirs overflows, customers’ service connections, etc

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PROBLEMS IN WATER SUPPLY DISTRIBUTION SYSTEM

• The problems normally faced in water supply distribution system are:
• Un-accounted for water (Leakage and Wastage of water),
• Degradation of quality of water,
• Reduction in carrying capacity, and
• Inadequate pressures at tail ends of the system
• Un-Accounted For Water
• Un-accounted for water (UFW) is the quantity of water, which is not

actually billed for and water charges for the same are not realized
from the consumers.
• The UFW water can be of two types:
• Physical loss (real losses) and
• Nonphysical loss (apparent losses)

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LEAKAGE LOSS

Physical Loss Apparent Loss

• Pipe bursts • Meter under registration
• Fittings • District meter error
• Joint leaks • Data handling error
• Communication pipe • Theft
• Authorized unmetered
leaks
consumption

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PHYSICAL LOSS

• Physical loss is the water actually lost through leakage and
wastage. Leakage is the water lost from storage reservoir,
transmission main, service reservoirs, and distribution system and
house service connections through leaks from cracks, holes or
joints of pipe lines and due to corroded pipes, and fittings in
house service connections. Wastage is the operational loss and
the wasteful use and misuse of water by the consumers.

• Wastage of water can also occur due to discarding of stored
water when fresh water supply comes in the case of intermittent
water supply system.

• Operational loss is the water used in the system for cleaning of
filter beds by back washing, sludge removal from clarifiers,
periodic cleaning of the service reservoirs, periodic flushing of
the deposits in the transmission mains and distribution pipes and
water lost during attending bursts, leaks and other repair works.

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NONPHYSICAL LOSS

• Nonphysical loss is the quantity of water lost due to the
mechanical errors in meters at the source, at various
points in the water supply system and at the
consumers’ connections, which are recording lesser
quantity of water than the actual quantity of flow.

• Human errors in reading or recording the meter reading
lesser than the actual quantity, and Flow through
illegal connections, which are not accounted and
billed for Nonphysical loss of water is considered as the
loss of revenue

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CAUSES FOR LEAKAGE

• The causes for the leakage in the pipeline could be
attributed to various factors as shown in

• The causes for the leakage in pipeline are due to the
following aspects also.

• The use of sub-standard pipes and fittings leads to imperfect
jointing, causing leakage in joints.

• Selection of pipe material with out considering the corrosives
of the soil in which the pipes are to be laid and the quality of
water the pipe have to carry, which eventually may lead to
corrosion of the pipes and fittings.

• Lack of quality control in jointing of pipes while installation,
which may result in leaks in joints when there is settlement of
the supporting soil.

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• Non-conducting or improper conducting of hydraulic
pressure testing of pipeline and joints at the time of
installation.

• Soil movement particularly when the pipes are laid in
swelling soils like clay, due to change of moisture content,
which may cause disturbance to the pipes and joints
ultimately resulting in leakage.

• Water hammer pressure disturbs the joints resulting in
leakage.

• Not detecting and rectifying the badly leaking joints
regularly. Even in a properly maintained system, at any time
10% of the joints will be seeping joints (with the loss of water
of 1 to 3 Lph / joint) and 1% of the total joints will be badly
leaking joints (with the loss of water of 90 to 200 Lph / joint).

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Leakage detection and repair
Leakage is a major component of NRW in many water supply systems
and therefore is a major focus when addressing NRW. By conducts a
strategic approach to reducing leakage, through the use of Visual,
Inspection and Sounding (VIS) and step testing techniques, as well as
the use of the latest technology available including leak noise loggers,
correlators and ground microphones.
Reservoir monitoring
Reservoir monitoring is a component of NRW that needs to be
continuously monitored and overflow experiences should be dealt
with as expediantely as possible to reduce the volume of water
lost and prevent reoccurance. The issue of reservoir
overflows/leaks through undertaking regular visual checks on all
reservoirs, installation of water level transducers to understand
the operation / critical levels of the reservoir, and servicing /
maintenance of altitude control valves/ball valves to ensure
optimum operation.

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CONTROLLING WATER
LEAKAGE AND WASTAGE

• Some of the following actions will be useful in
controlling the leakage and wastage.

During construction:
• metering of all consumers’ connections,
• introduction of realistic tariffs,
• use of non- corrodible quality materials for house

service connections.

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DURING OPERATION AND
MAINTENANCE

•checking domestic water meters every year and recalibrate
to keep the error within 3%,
•replacing the water meters once in 6 years,
•repairing and replacing consumers’ leaky service pipes free
of charge wherever necessary,
•visits to large consumers’ premises and audit their water
usage and identify the source of wastage,
•legal action for illegal connections,
•establishing regular program for leak detection survey, and
•Intensive publicity campaign on conservation of water.

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PIPELINE LEAK
DETECTION

❑Detecting water pipe leaks is normally done acoustically or
by filling the pipe with a tracer gas and using sensors to see
where the gas escapes.
❑Part of the process of water pipe leak detection is tracing
the location of the pipe. Our engineers carry a large range of
equipment which allows us to accurately trace metallic or
plastic pipes.
❑Some pipe leak detectors can be inserted through the pipe
which will allow us to pinpoint the leak and trace the line of
the pipe.
❑Water pipe leaks can often be located with little or no
disruption to the clients water supply or operations. Were an
interruption to the water supply is not acceptable we can
locate and repair the leak without turning the water off.

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PIPELINE LEAK
DETECTION

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ACOUSTIC LISTENING

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SOUNDING

Sounding is a systematic survey and
is a non-intrusive method of
"listening" for water leak sounds on
valves, hydrants and stop-taps in
underground, pressurized pipes when
there is no obvious evidence of water
surfacing in a yard or flowing on the
street.

The basic instrument is the Electronic
Listening Stick, which is used as a
simple acoustic instrument
electronically amplified. This
technique is still widely preferred by
the majority of practitioners.

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SMS DATA LOGGER

Since commencement of Concession Agreement, substantial investment has been
made to procure electronic equipment for active leak detection. These include
ground microphone, leak noise correlator, leak noise logger with SMS features,
integrated digital logging and correlating system and insertion probes. The
deployment of high tech equipment combined with specialist know-how,
underground leaks have been located for quick repair to reduce physical losses on a
cost effective basis.

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Corelation is a way of finding and pinpointing leaks in water pipes.
Leak sounds are pinpointed to the closest probable location using
computerized correlation technology.
The transmitters from a Water Leak Correlator system are set up in
different configurations on hydrant, mainline valves and accessible
metal parts of the network. Correlations are conducted at each setups
and the leak position is confirmed and located.

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GROUND MICROPHONES

• Ground microphones allow
us to amplify, trace and
display the noise created by
a water escaping from a
pipe. We also use ground
microphones to trace the
line of a pipe. This is done by
inducing a sound wave
along the pipe which can
be measured at ground
level thus allowing us to
follow and plot its route.

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GROUND MICROPHONES

The technique involves placing the microphone on the ground at
intervals along the line of the pipe and noting changes in sound
amplification as the microphone nears the leak position. Using a ground
microphone attachment to an electro-acoustic instrument re-confirms
the location of the leak

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