Water distribution system
The information used to describe a water distribution system can be obtained by undertaking an analysis of your existing water distribution system.
An analysis should assist in the development and implementation of a WRMP that is both efficient and cost effective. It should consider the entire water supply process from source water (water entering your facility or collected by the facility itself), to storage and pipework infrastructure, to points of use within your facility.
A comprehensive analysis may also enable the identification of areas of potential or increased risk from hazards or hazardous events, including possible control and monitoring points within your water distribution system.
Water entering a facility may be supplied by a local government or state-owned water utility or the facility may have its own private water supply, such as a private bore or rainwater tank.
Some facilities may also have more than one water source, for example, potable water from the town water supply and non-potable water from an onsite groundwater bore. Non-potable water sources should be included in your WRMP if the source may contain microbial or other hazards and there is a possibility of vulnerable patients or residents being exposed to the water, or aerosols from the water.
Having a good understanding of the source and quality of water entering your facility will influence the management of risks and controls associated with the growth of Legionella and other water‑related hazards.
Existing information about your source water may be available from your drinking water service provider, via their website, or you may have to contact them directly. The following information should be sought:
- the (initial) source of the water entering your facility e.g. dam, river, or underground (deep artesian bore or a shallow aquifer)
- the water treatment applied and type of disinfection used, if any
- the nearest disinfection point, the frequency at which it is monitored and the typical free chlorine residual or other disinfectant residual in the water at or close to the point where the water enters your facility.
- the town water storage capacity in treated water reservoirs, and the likely length of time that it could supply your community if the town water treatment plant failed
- the temperature of the water (particularly bore water) in the water reticulation system at your point of connection
- any Australian Drinking Water Guideline health values regularly or occasionally exceeded, e.g. Escherichia coli (E. coli) or trihalomethanes (a common by-product when water is disinfected using chlorine)
- any other aspect of the quality of the water entering your facility that may affect the safety of the water used in your facility (e.g. for kidney dialysis machines)
- the communication methods used by your drinking water service provider to notify customers of boil water alerts, interruptions to supply, and other water incidents
- the location of the entry point(s) to your facility and their position relative to the town water supply point(s).
Facilities that receive water from their own private water supply (for example rainwater tanks or bore water) may not have the information described above about their source water. They will therefore need to undertake further water quality analysis in order to establish the extent to which they will require additional management and control measures (For further information on the management of rainwater tanks, see enHealth – Guidance on use of rainwater tanks).
Water within your facility
Accurate existing plans of the water distribution system within your facility may provide some useful information, but obtaining such plans for larger and older buildings can be difficult. An experienced plumber can often provide additional insight into the location of water infrastructure.
The description of the water distribution system should include the following information:
- the sources of water used at the facility (reticulated potable, reticulated non-potable, reticulated recycled, locally recycled, roof-harvested (rain) or surface water (stormwater)
- the water distribution system for each source of water within the facility, including hot, cold and warm water system
- water storages on your facility for any of the water sources
- any water treatment, other than heating, of the water
- water distributed between buildings within a multi-building facility complex
- how water is distributed within each building, including any return loops
- the number and type of outlets within a facility
- location of infrastructure such as water meters, stop valves and backflow prevention devices
- if the building has a cooling tower, how the water is supplied to and drained from it
- whether the fire suppression (sprinkler) system water has a separate water source, and if not, what backflow prevention is installed, if any
- whether an irrigation system (e.g. watering systems for pot plants or gardens) uses the main potable water supply. If it does, is a backflow prevention device installed, and if not, what is the source of irrigation water?
- the method used for heating water, its capacity and location
- the existence of water disposal systems other than to the sewer system.
A flow diagram can be used to represent the information described above.
It is important that all uses of water within the facility are identified. Uses include, but are not limited to:
- potable water uses (drinking, bathing and food preparation, including ice machines and cold water dispensers)
- clinical uses (e.g. maternity, intensive care), including dialysis, dental chairs and heater cooler perfusion devices.
- sterile or boiled water uses, such as nebulizers and CPAP devices
- potable or non-potable water uses, such as toilet flushing, laundry or outdoor irrigation
- uses requiring additional disinfection including hydrotherapy, swimming and spa pools, birthing pools
- fire-fighting and fire suppression uses, including sprinklers
- air conditioning uses, including evaporative air conditioners
- decorative fountains or water features.
An inventory can be a useful way to capture this information.
- National enHealth guidelines for Legionella control (PDF, 577KB) – section 2.1.1 (pages 8 to 9)
- enHealth Guidance on use of rainwater tanks (PDF, 587KB)
- Australian Drinking Water Guidelines Paper 6 National Water Quality Management Strategy
- McCoy, W. F., 2005. Preventing Legionellosis. IWA Publishing, London.