Backflow and garden irrigation in Sydney

Terms on a plumber’s report

Sydney Water’s glossary, in our words:

Backflow

Flow against the normal or intended direction: water from a source that may be polluted running into a drinking water supply.

Backsiphonage

What happens when the pressure of the water supply drops below atmospheric pressure.

Cross-connection

Any link between the drinking water system on the main and a fixture that could, in some conditions, let non-drinking water or other substances into that system.

Backflow prevention device

A device that stops backflow. There are several kinds, among them the reduced pressure zone device, the registered air gap and the testable double check valve.

Licensed plumber

A plumber holding a licence issued by Building Commission NSW.

Water meters

On a site with a low hazard rating, Sydney Water’s 20 mm and 25 mm water meters already have a backflow prevention device built in. A property whose meter is larger than 25 mm needs a containment device of its own, separate from the meter. A licensed plumber must assess each site to work out its backflow containment needs.

While a garden is being built, the site has one more rule: the water supply on every construction site must have a backflow containment device.

Rainwater tanks

Sydney Water’s rainwater tank rules, in our words

Set-up	What Sydney Water requires
Above-ground rainwater tank	Counted as low hazard. With a 20 mm or 25 mm meter, no further backflow prevention is required.
Below-ground tank taking rainwater only	A vented dual check valve with an atmospheric port.
Stormwater, greywater and other alternative supplies	Counted as high hazard.

Assessment and testing

Sydney Water’s page places these duties on the plumber:

• A licensed plumber assesses the site to work out its backflow containment needs.
• The plumber tells the owner what those needs are, and installs a device that matches the property’s hazard rating.
• The plumber also tells the owner whether the device needs testing every year.
• Once installed, the device is tested by a backflow-accredited plumber and registered straight away.
• After each test, the plumber lodges the test report through Sydney Water’s Backflow Prevention system.

Sydney Water audits these lodgements and may ask for two photographs of any registered test: the tested device with its serial number clearly visible, and the test kit used. Zone and individual backflow devices are not registered on its portal; questions about them go to Building Commission NSW.

Plumbing licences

Among the work NSW Fair Trading says needs a licence is “all specialist work regardless of its cost,” and it explains that “Specialist work includes electrical wiring, plumbing, drainage and gasfitting work and air conditioning and refrigeration work (except plug-in appliances).” So the $5,000 threshold explained in the structural landscaping licence guide does not apply to the plumbing in a garden job.

Irrigation and the watering rules

Garden irrigation meets two sets of Sydney Water rules. Under the Water Wise Guidelines, drip irrigation and smart watering systems may run between 10am and 4pm, when other watering with drinking water may not. And rainwater from a tank that holds no drinking water sits outside those guidelines altogether. On the backflow side, it is the licensed plumber’s assessment of the whole site that sets its containment needs, and those needs follow its hazard rating. The full watering rules are in Sydney Water’s water rules.

A pool on the same lot has barrier rules of its own, in pool barriers in NSW, and the backyard plan shows every guide in place.