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DesignofWaterSupplyNetworks
CIVL5995ProjectI
AhmadSana
DepartmentofCivilandArchitecturalEngineering
SultanQaboosUniversity,Oman
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Designof
water
distribution
system
Amunicipalwaterdistributionsystemisusedtodeliverwatertothe
consumer.
Wateriswithdrawnfromalongthepipesinapipenetworksystem,for
computationalpurposesalldemandsonthesystemareassumedtooccur
atthejunctionnodes.
Pressureisthemainconcerninawaterdistributionsystem.Atnotime
shouldthewaterpressureinthesystembesolowthatcontaminated
groundwatercouldenterthesystematpointsofleakage.
Thetotalwaterdemandateachnodeisestimatedfromresidential,
industrialand
commercial
water
demands
at
that
node.
The
fire
flow
is
addedtoaccountforemergencywaterdemand.
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Componentsofawaterdistribution
system
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FunctionalComponentsofaWaterUtility
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Largediameterwatermains
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PressureReducingandCheckValve
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ATypicalPumpingStationSchematic
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Pumphouse
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Centrifugalpumps
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Typicalelevatedwater
tanks
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Reservoirpumptanksystem
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Pumpcurves
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Typesofvalves
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Typicallayoutofwatersupplysystem
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Usingboosterpumps
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Operationofawatersupplysystem
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Systemheadcurve
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Pumpoperatingpoint
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Operatingpoints(Max.and Min.)
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Operatingpointsforvariouspumps
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Operationpointsforvariouspipes
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Typicalpipenetwork
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WaterDemandTotalwaterdemandatanodeisequaltotheaveragewaterdemandper
capitamultipliedbythepopulationservedbythatnode.
Thepopulationmaybeestimatedbyanyoftheavailablemodelsof
populationgrowth.Thesemodelsusethepreviouslyavailablepopulation
data
for
future
projections.Forexample,accordingtoArithmeticmodel:
P(t)isthepopulationattimetandP0isthereferencepopulation.
ktPtP 0)(
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Public Authority for Electricity and Water, Sultanate of Oman
DesignGuidelinesandStandardsforWater
SupplySystems
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Demandpattern
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FiredemandInsurance Services Office, Inc. (ISO, 1980) formula: iiii PXOCNFF )( where, NFFi is needed fire flow at location i, Ci is the construction factor based on
size and type of construction of the building, Oi is the occupancy factor reflecting
the kinds of material stored in the building (value range from 0.75 to 1.25), and
(X+P)i is the sum of the exposure factor and communication factor that reflects the
proximity and exposure of other buildings (value range from 1.0 to 1.75).
ii AFC 220min)/L(
Ai is the effective floor area in square meters, typically equal to the area of the
largest floor in the building plus 50% of the area of all other floors, F is a
coefficient based on the class of construction. The maximum value of Ci and
typical F values are given below:
Classof
Construction
Description F Max.Ci(L/min)
1 Frame 1.5 30,000
2 Joisted masonry 1.0 30,000
3 Noncombustible 0.8 23,000
4 Masonry, noncombustible 0.8 23,000
5 Modified fire resistive 0.6 23,000
6 Fire resistive 0.6 23,000 34
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FiredemandCombustibilityclass Examples Oi
C1 Noncombustible Steel or concrete products storage 0.75
C2 Limited combustible Apartments, mosques, offices 0.85
C3 Combustible Department stores, supermarkets 1.0
C4 Freeburning Auditoriums, warehouses 1.15
C5 Rapid burning Paint shops, upholstering shops 1.25
Average value of (X+P)i is 1.4. The NFF should be rounded to the nearest
1000L/min if less than 9000 L/min and to the nearest 2000L/min if greater than
9000L/min.Requiredfireflow(L/min) RequiredfireflowDuration(h)
140 kPa
Maximum pressure (not strict) : 650kPa.
Storage facilities1. 20% to 25% of the maximum daily demand volume
2. Fire demand3. Emergency storage (minimum storage equal to average daily system demand)
4. Minimum height of water in the elevated storage tank based on minimum
piezometric head in the service area
5. Normal operating range 4.5 to 6.0 m.
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