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Building and renovation

Backflow protection

When it comes to Canberra's water network, all drinking and recycled water connections must have backflow containment protection. This reduces the backflow hazard your property might pose to our supply.

Property owners are responsible for ensuring the correct backflow prevention device has been installed on their water service. As such, each property’s backflow prevention requirements need to be assessed by a licensed plumber or hydraulic consultant.

What is backflow?What is backflow containment protection?
How can backflow occur?Who can assess, install and test for backflow prevention?


We provide a backflow prevention device for 20 and 25mm water meters in the form of integrated non-testable dual check valves. While these integrated check valves provide adequate low-risk backflow protection, they may not necessarily meet the minimum backflow requirements for every type of property. For example, this backflow protection is insufficient for industrial and commercial operations or residential properties that make use of medium or high-risk appliances/activities.

Meters larger than 25mm do not include backflow prevention devices. For these meters/services an appropriately licensed plumber is required to assess and apply the correct backflow preventative measures appropriate to the property’s hazard ratings. Some backflow-prevention devices are testable and must be checked regularly by a licenced person endorsed for backflow testing.

Testing backflow-prevention devices
All testable backflow devices must be registered with Access Canberra at the time of installation. This is so they can be tracked and managed.

Testable backflow-prevention devices are those that include features to allow testing in-situ, i.e. without the need to remove the device. Backflow-prevention devices must be installed by an appropriately qualified licensed plumber and tested every 12 months (in line with AS/NZS 3500 and AS/NZS 2845.3:2020). 

What is backflow? 
The unintended reversal of water flow from a potentially contaminated source into a drinking water supply, such as the water supply network, is termed backflow. Safety impacts can range from a minor nuisance to endangered health or even death. 

What is backflow-containment protection?
A backflow-prevention device installed downstream of the water meter, but before any branches or connections, is a backflow-containment device. It is designed to stop water from flowing back into the water supply network.

How can backflow occur? 
Backflow may occur when the pressure in a main is lower than the pressure within a customer’s property. While our systems are designed to avoid pressure differentials, there is still a risk they may occur. This unintended variance is caused by any events that move water from the consumer pipework into the water main, such as:

  • Back siphonage - a sudden drop in water main pressure caused by pipe failure.
  • High demand – high usage due to fire-flow extraction or a bushfire emergency.
  • Back pressure – higher pressure in the customer plumbing (which may incorporate pumps) that forces the flow of water in reverse.  

Who can assess, install and test for backflow prevention?
Only licensed plumbers with backflow-prevention accreditation (issued by a registered training organisation) can assess your properties backflow requirements and install, commission or test backflow devices.

Our organisation takes water quality management very seriously. We partner with the Water Services Association of Australia (WSAA) and Access Canberra to ensure we are up to date on a range of topics, including backflow prevention and cross contamination.