ce 370 - design layout of distribution systems

8/2/2019 Ce 370 - Design Layout of Distribution Systems

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DESIGN LAYOUT OF

DISTRIBUTION SYSTEMS

CE 370


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Distribution System Layout

Layout of water distribution system is a function

of:

source of water supply

topography of distribution area

variation in water consumption


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Source of Water Supply

water is supplied at one point (i.e. treatment plant)

distribution storage (elevated tank or

ground-level tank plus booster pump) is

required in remote areas to maintain water

pressure

water is supplied at several points (wells)

storage capacity is reduced and pipe sizes

required are smaller.


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Topography

water is supplied at high elevation

it flows by gravity through the water

network.

water is supplied at low elevation

must be pumped up into the water

network (pipes and storage).


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Water Consumption

is a function of residential, commercialand industrial demands.

planning and zoning is applied to controlvariations in water consumption.

Climate and economical aspects could alsoinfluence the layout of a water distributionsystem.


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The objective of an engineer designing a

water distribution system is to provide astable hydraulic gradient to maintain

adequate pressure throughout the service

area and enough pumping and storage

capacities to meet emergency demands.

The following figure shows simplified water

distribution systems which illustrate the basic

principles of design.


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EVALUATION OFDISTRIBUTION SYSTEMS


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Quantity

the water source plus the storage facilitiesmust be able to provide enough water to meetboth current and future demands (ten years

ahead).

records of average daily, peak daily, peak

hourly rates of consumption of the past tenyears are needed, beside other factors relatedto community growth, to project the futureneeds.


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Intake Capacity

surface water intakes must be large enough to

deliver enough water to meet municipal use

and treatment plant needs during any day of

peak demand.

if storage is not available, water intake

capacity must be large enough to meet fire

demand, maximum hourly flow, and inplant

process needs at the same time.


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Pumping Capacity

Low-lift pumps transport water from the source to the treatment plant.

High-lift pumps transport water from the treatment plant to the distributionsystem.

Well pumps deliver water to the treatment facilities or directly to thedistribution system.

Booster pumps are needed to increase pressure in the distribution system oflarge communities or in areas with widely varying elevations.

Pumping stations must have enough capacity to provide the amount ofwater at flow and pressure rates needed to meet both daily and hourly peakdemand plus fire flow.

Pumping stations must be reliable through duplication of units, standbyequipment, and alternate sources of power


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Piping Network

Arterial and secondary feeder mains must be designed to supply waterservice for 40 or more years after installation.

Actual lifetime of pipes of mains under normal conditions is 50 to 100years.

Sub-mains must be at least 6 inches in diameter in residential districts and 8inches in important districts.

Distribution lines are laid out in gridiron pattern

Avoid dead-ends

Adequate number of valves must be installed to allow shutoff in case ofemergency

Valves should be located in a way so that no more than one block will be

out of service in case of emergency.

ce 370 - design layout of distribution systems

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