Water normally flows from Power and Water’s pressurised water supply system to your property. If pressure drops in the water supply system, it’s possible for water to flow in the reverse direction. This backflow has the potential to contaminate drinking supply.
A severe backflow incident can endanger health and, in extreme cases, threaten a person’s life.
Backflow can occur if:
- a break in a water main causes water supply system pressure to drop
- a large volume of water pumped from the water main during a fire, causes water supply system pressure to drop
- a pump connected to your system or high pressure from your system causes a reverse flow.
All premises must comply to current Australian Standards for backflow prevention.
There have been many backflow incidents around the world including the Northern Territory. In 2004, an incident occurred at a uranium mine in Kakadu where workers were exposed to water contaminated with uranium and acid, due to the mixing of potable and contaminated water. One of the key causes of this incident was that there was no backflow prevention in place at the cross connection of the two systems.
A backflow accredited plumber or qualified water industry representative must assess your property and define the “Hazard Level”. Property owners with premises identified as being a “High” or “Medium” hazard level must install and test a backflow prevention device at the water meter.
Your plumber must also test this device annually and forward the test reports to us. We’ll maintain a register of all testable devices installed at your property boundary. We'll advise you in writing when your equipment is due for its annual test.
Where properties have a Power and Water potable supply only, Power and Water supply and install a 20-25 mm water meter that incorporates an integrated dual check valve assembly. This means if a property is assessed as low hazard with 20/25 mm water meter, no other prevention is required to be installed. The backflow accredited plumber must however, submit a low hazard assessment form, for commercial and industrial premises deemed as low.
There are a number of approved devices available, including:
- a break tank with a registered air gap
- Reduced Pressure Zone Device (RPZD)
- Double Check Valve (DCV)
- Dual Check Valve (DuCV)
- Single Check Valve Springs Loaded - Fire Services only (SCVT)
- car and factory washing facilities
- chemical plants, factories or dispensing facilities
- commercial laundries
- hospitals, mortuaries, autopsy facilities, clinics,
- funeral parlours
- premises with boiler, chiller or cooling tower makeup water system
- premises with an alternative water supply
- veterinary clinics and similar facilities
Medium risk installation
- caravan parks
- commercial swimming pools, spas and fountains
- food and beverage processing plants
- irrigation systems on non-domestic properties
- secondary school laboratories
Low risk installation
- Hair salons or troughs
- In-line water softeners and water filtration equipment
- Irrigation systems on residential properties
- Private bores of known water quality on residential properties
- Rain water tanks on residential properties
- Photographic processing machines (no developer mixing)