Presentation on theme: "Describe a water supply distribution system"— Presentation transcript:
1 WATER SUPPLY DISTRIBUTION On completion of this module you should be able to Describe a water supply distribution systemdescribe the components of pipe distribution systemsappreciate the Queensland Planning Guidelines for Water Supply and Seweragedesign simple gravity and rising mainsdetermine the required storage capacities and location in a water supply distribution
2 WATER DISTRIBUTION SYSTEMS A network of pipes & storage tanks to meet demand at satisfactory pressureGrid or branching layoutSupply zones and storage tanksDesign flow rates
6 Design of Urban Water Supply Schemes Trunk main from headworks to distribution reservoirs must cater for MDMM capacitySupply mains from service reservoirs and reticulation network must achieve MH demandMaximum pressure 80 m head in pipelinesMinimum pressure 22 m (12 m under firefighting)
7 Some design parameters Annual demand is the total demand for a community, ML/yearAverage daily demand (ADD) = Annual demand/365, ML/dMean day maximum month (MDMM) = 1.5 x ADDMaximum day (MD) = 1.5 x MDMMMaximum hour (MH) = MD/12 or x ADD/12
8 Design of Gravity Main Determine the maximum capacity Select pressure at load centre, check for pressure at high and low pointsAscertain TWL of service reservoir and total lossesStatic head must not be excessive. Consider adjusting elevations or introduce break-pressure tankDesign for appropriate pipe diameter through a process of iteration
10 Maximum capacity This depends on the location of the delivery system For trunk main from the headworks to the distribution storage tank, the design capacity is MDMMFor other mains and within the reticulation system, the pipe must be designed to carry the maximum instantaneous flow i.e. MH demand.
11 Hydraulic equations Use Darcy-Weisbach and Moody equations Determine the head losses (friction and minor)Friction loss = f L v2 /(2gD)
12 Design of Rising Main Operating hours must be less than 24 hours Operating cost and not construction cost may be a significant factorPump power is directly related to head losses which increases with the square of flow velocityUse economic analysis
13 Service ReservoirProvides adequate pressure and acts as a buffer between supply and demandOperating storageBreakdown storageFirefighting
14 Types of Service Reservoirs Surface tankStandpipeElevated tank
15 Location of Storage Reservoir Storage reservoir is an essential component of a distribution system. A strategic location is important in terms of cost and serviceLocate centrally and as close as possible to the area it serves to minimise head losses and capital construction costsLocate at an elevation (natural or constructed) high enough to provide adequate pressuresTo accommodate fluctuation in demand, high and low supply operations regimes are to be provided
16 Reservoir location influences pressure distribution
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