1. WATER SUPPLY DISTRIBUTION On completion of this module you should be able to
Describe a water supply distribution system
describe the components of pipe distribution systems
appreciate the Queensland Planning Guidelines for Water Supply and Sewerage
design simple gravity and rising mains
determine 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 pressure
Grid or branching layout
Supply zones and storage tanks
Design flow rates

3. Reticulation pipe networks
Branching system
Grid system
Reticulation pipe networks

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

5. PIPE APPURTENANCES

6. Design of Urban Water Supply Schemes
Trunk main from headworks to distribution reservoirs must cater for MDMM capacity
Supply mains from service reservoirs and reticulation network must achieve MH demand
Maximum pressure 80 m head in pipelines
Minimum pressure 22 m (12 m under firefighting)

7. Some design parameters
Annual demand is the total demand for a community, ML/year
Average daily demand (ADD) = Annual demand/365, ML/d
Mean day maximum month (MDMM) = 1.5 x ADD
Maximum day (MD) = 1.5 x MDMM
Maximum 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 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

9. Design of Gravity Main

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 MDMM
For 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 factor
Pump power is directly related to head losses which increases with the square of flow velocity
Use economic analysis

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

14. Types of Service Reservoirs
Surface tank
Standpipe
Elevated 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 service
Locate centrally and as close as possible to the area it serves to minimise head losses and capital construction costs
Locate at an elevation (natural or constructed) high enough to provide adequate pressures
To accommodate fluctuation in demand, high and low supply operations regimes are to be provided

16. Reservoir location influences pressure distribution

17. Use of rise and fall main

18. End of Module 19 - Water distribution systems