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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.