WATER SUPPLY DISTRIBUTION On completion of this module you should be able to

1. WATER SUPPLY DISTRIBUTIONOn completion of this module you should be able to • Describe pipe structures, types and installation • design gravity and rising mains • have an understanding of pipeline economics • appreciate the Queensland Guidelines for Planning and Design of Urban Water Supply Schemes • describe the components of pipe distribution systems • determine the required storage capacities and location in a water supply distribution

2. STRUCTURAL PIPES • Pipes may be broadly classed as rigid or flexible • non-pressure to accommodate external loads only • pressure pipes will accommodate internal and external pressures • Types of pipes e.g. concrete, AC, clayware, plastic, ductile iron and steel • pipe joints may be rigid or flexible e.g. Spigot-socket, push-on, mechanical, flanged etc.

3. PIPE JOINTS (a) Spigot-socket (b) push-on (c) mechanical (d) flanged (e) ball (f) threaded (g) victaulic (h) gibault

4. PIPE INSTALLATION • Australian Standards apply e.g. AS3725-1989 Loads on buried concrete pipes • trenchless technology (no dig) reduces social, economic costs of street disruption • integrity testing e.g. water testing and low-pressure air testing

5. TRENCHLESS TECHNOLOGY

6. PIPE APPURTENANCES • Stop, butterfly valves • reflux or non-returning valves • pressure reducing, pressure sustaining valves • pressure relief valves (surge) • air valves • hydrants

7. PIPE APPURTENANCES

8. PUMPS • Radial flow (centrifugal) for moderate flows against high heads • axial flow (propeller) for high flows against low heads • mixed flow (partly radial/axial)

9. PUMP CHARACTERISTICS AND OPERATIONS • Pump head versus discharge • a constant speed pump is designed to operate at or near best operating point (BEP) • system head versus discharge • pump power usage and operating costs are dependent on pump and motor efficiencies • check the NPSH

10. DISTRIBUTION SYSTEMS A network of pipes & storage tanks to meet demand at satisfactory pressure • Grid or branching layout • Supply zones and storage tanks • Design flow rates

11. DISTRIBUTION SYSTEMS Branching Grid

12. Guidelines for Planning & Design of Urban Water Supply Schemes • Trunk main from headworks to distribution reservoirs must cater for MDMM capacity • Supply mains and reticulation network must achieve Peak hour (PH) demand • Maximum pressure 80 m head in pipelines • Minimum pressure 22 m (12 m under firefighting) Note in 2005, the Planning Guidelines for Water Supply and Sewerage replaced The above guidelines

13. Design of Gravity Main • Determine the maximum capacity • Select pressure at load centre, check for pressure at high and low points • Ascertain TWL of service reservoir and total losses • Static head must not be excessive. Consider adjusting elevations or introduce break-pressure tank • Design for appropriate pipe diameter through a process of iteration

14. Pipeline Economics • Capital costs • Operating cost (recurrent expenditure) • How does one compare the costs of various options?

15. How does one compare the costs of various options? • Equivalent annual cost method • Present worth method

16. Design of Rising Main • Operating hours must be less than 24 hours • Operating cost and not construction cost may be a significant factor • Pump power is directly related to head losses which increases with the square of flow velocity • Use economic analysis

17. Service Reservoir Provides adequate pressure and acts as a buffer between supply and demand • Operating storage • Breakdown storage • Firefighting

18. Types of Service Reservoirs • Surface tank • Standpipe • Elevated tank

19. Surface Tank Capacity • 3 (PD - MDMM) • Sustain 3 x consecutive PD for system Note in 2005, the Planning Guidelines for Water Supply and Sewerage replaced the Guidelines for Planning and Design of Urban Water Supply Schemes and the above equations may not be used

20. Elevated Tank Capacity • 6 (PH - MDMM/12) + fire fighting reserve • Sustain 6 x consecutive PH for system • Supply main to tank to carry in 6 h, the capacity equal to (6 x PH less operating storage) Note in 2005, the Planning Guidelines for Water Supply and Sewerage replaced the Guidelines for Planning and Design of Urban Water Supply Schemes and the above equations may not be used

21. System Capacity/Performance • At ADD, the system should fill all reservoirs from empty to full within 5 days of continuous operation • During MDMM demand, each reservoir should have a net inflow • During 3 days consecutive PD demand, reservoirs should not empty

22. System Capacity/Performance (cont.) • During PH demand, min pressure of 22 m and capable of supply 6 consecutive MH • Fire flow of 30 L/s in commercial and 15 L/s in residential areas, in addition to a base flow of 2/3 PH. • At fire fighting demands, minimum pressure  12 m

23. Ideal location of service reservoir • Locate close and central to load centre • High elevation to maintain adequate pressure • Use of rise-fall main if siting of service reservoir is further

24. Location of storage reservoir

25. Use of rise and fall main

26. END OF MODULE 3