Backflow prevention

Installing a backflow prevention device can protect our water supply.

Backflow is when water from your property is drawn back into the water mains. This happens when the pressure in water pipes is reduced. If this water is contaminated, it can risk the safety of our water supply.


The flow of water into your property is generally maintained at a consistent pressure. This is so water can flow consistently from your taps, shower, hose and other fixtures.

There are times when the normal water pressure is reduced – for example, when a water main bursts. When we repair the damage to the burst pipe, the remaining water can drain out. This can create a type of vacuum-effect on the water supply. This means that water can flow back into the water main from nearby properties. This is backflow.

Backflow can also happen when there is high demand on the water system – for example, when multiple fire hydrants are being used.

Reported backflow situations are rare. However, they have the potential to be a significant risk to our infrastructure and customers.

Backflow prevention device

Backflow can be prevented by installing a backflow prevention device (BPD) at the outlet of your main water meter. This device only allows water to enter your property through the water meter. It prevents water from flowing back into our water supply system.

When you connect your property to our services, we assess the risk of backflow. If the hazard risk of your property is assessed as high or medium, then you must install a BPD. Some existing properties or connections are also required to install a BPD.

Properties with a high or medium hazard risk are generally commercial and industrial, not residential. Most residential properties are considered low-risk properties. These properties have a water meter with a dual check valve.

A duel check valve allows water to flow in one direction – to your tap – by forcing a spring open inside the valve. If water starts to flow in the opposite direction – back into your home – the spring closes, preventing this from happening.

Register a backflow prevention device

If your property is a high-risk or medium-risk property with a BPD, you must be registered with us.

How to register

To register, you need to complete a registration and agreement for a BPD.

You can submit your application:

  • by email to
  • by post or in person at our office.

We’ll get back to you within 5 days.

If we need more information, we’ll contact you.


The fee for 2024-25 is $188.80 (excl. GST). Contact us to pay by credit card.


As the owner of a property with a BPD, you must:

  • comply with our Backflow Prevention Containment Policy and the laws and standards mentioned in the policy
  • get a licensed plumber to install the device to comply with AS/NZS3500 requirements
  • make sure the device is tested annually by a licensed plumber – by the due date and following the manufacturer’s instructions
  • email the results of each test to us within 20 days to
  • record the date of the test and the dates of any maintenance work.