Backflow prevention

All connections to our water and recycled water pipes must be protected with backflow prevention containment devices. This includes fire service connections. 

A backflow prevention containment device on a business customer's site.

Backflow prevention containment devices stop potentially contaminated water from flowing back into our water pipes.

Backflow occurs when water from a customer's property flows backwards into our pipes. This may carry contaminants that can harm people's health.

Backflow is more likely to occur if:

  • there's a drop in pressure in the main, eg during a main break
  • water pressure at the property is higher than at the main, eg if a pump is operating on the site.

Contaminants may enter the drinking water system through a cross connection caused by:

  • faulty plumbing
  • hoses submerged in buckets, tanks or pools.
Contaminated water can pose serious risks

Contaminants may include chemicals, oil, bacteria, mud and debris.

Backflow prevention devices stop water flowing back into our pipes.

Backflow prevention devices have one of the following elements to stop water flowing backwards:

  • a valve that only lets water go in one direction
  • an air gap
  • a break tank.

These devices are important as they protect our water quality - and the health of people using it.

Property owners are responsible for getting the right kind of backflow device installed.

If you're the property owner, you must ensure that:

  • you have the right kind of backflow prevention device installed at your property
  • the device is properly maintained. 

What do you need to do?

Assess the hazard rating 

You must engage an accredited backflow plumber to assess your site's hazard rating. The hazard rating needs to be assessed every time site activities change. 

Tell your plumber if your property has more than one connection to our water main. This may affect your hazard rating and the type of device the plumber must install.  

Install the device 

You must get a licensed plumber to install the right kind of device. 

You're responsible for ensuring your plumber sends us a certificate of compliance when they install high and medium hazard devices.

Test the device

Your accredited backflow plumber must test high and medium hazard devices:

  •  when they're installed
  •  every year after the device is installed.

Send us the results

Ensure your accredited backflow plumber sends us the results within two days of the test.

Your backflow device must be suitable for your property's hazard rating.

Your accredited backflow plumber will assess your rating.

Examples of hazard ratings for different businesses are shown in the Australian Standard, AS/NZS 3500:1.

What type of device do you need?

Low hazard properties

Owners of low hazard properties must get a non-testable backflow prevention containment device installed.

Our 20 and 25 mm meters have a simple backflow prevention device in them. These are suitable for low hazard connections.

You must get a separate device installed if you have:

  • a larger meter
  • an unmetered water connection
  • a high or medium hazard rating.

Medium hazard properties

Owners of medium hazard properties must get a testable double check valve assembly installed. 

High hazard properties

Owners of high hazard properties must get a registered break tank, reduced pressure zone or registered air gap installed.

Metered standpipes

If we've given you permission to use a metered standpipe on our pipes, your standpipe must have a testable double check valve incorporated into its design.

Construction sites

You need a backflow prevention device on water main connections you use for construction and renovation.
If you're building more than a single stand-alone house, we consider it to be a high backflow hazard.

Sprinkler and fire services

If your property has separate sprinkler and fire services, you must get a testable double check detector assembly. It must be installed near where the water service enters your property or upstream of any booster assembly or off-take from the fire service.

If your property has a window or wall drencher system, you must install a non-testable low hazard device.

Unknown hazard rating

If you don't know your site's hazard rating, or don't get it assessed, we'll assume it's a high hazard.
Owners of properties with unknown hazard ratings must get a registered break tank, reduced pressure zone or registered air gap installed.

You must use accredited backflow plumbers and licensed plumbers.

An accredited backflow plumber must assess your site's hazard rating and test your backflow device. You can select an accredited backflow plumber from our list.

A licensed plumber must install your device. NSW Fair Trading licenses plumbers in NSW.

We keep a register of all installed testable backflow prevention containment devices. We'll remind you when it's time to get your backflow device tested each year.

We audit a sample of installations to make sure they comply with Australian Standard AS/NZS 3500:1.

If your installation doesn't comply with the standard, we'll issue you with a notice to repair, maintain, test or replace the device.

If you don't comply with our backflow requirements or notices, we may:

  • restrict your water supply
  • disconnect you
  • charge you any costs we incur to make your connection satisfy our requirements.

Does your business need a backflow plumber?

A motor industry repair business.

We can help you find a backflow accredited plumber in your area.

Search for a backflow plumber

Does your plumber need to submit your report?

A backflow device suitable for medium hazard properties.

Plumbers can send backflow reports to us online.

Register for a Backflow web lodgement account