Backflow Prevention

What is backflow?

Backflow is the unintended “backwards” flow of water from a potentially polluted source into a potable water supply.

What is backflow prevention?

A backflow prevention device stops backwards pipe flow and protects us from drinking or using contaminated water.

How does backflow occur?

Water supply systems are designed to ensure that water flows to the property under pressure. If this pressure is less than the pressure at the property, there is a high probability that water could be drawn back into the potable water supply system. Backflow or syphonage can occur when:

  • there is a break in the water main (internally within the property or externally in Council’s pipe network) and water syphons backwards from the polluted water into the supply pipe
  • water is being pumped from the main water supply during a fire
  • a customer is using water at a higher pressure than the pressure supplied
  • heavy water use on site reduces water pressure within the water’s supply network
  • the water outlet on the property is substantially higher than the water main

What contamination could be in backflow?

Potential pollutants to the water supply from backflow incidents can be of many types.  The nature of the polluted water largely depends on the nature of the business use.  For example a fire in a business that uses chemicals has a high risk of those chemicals potentially entering the water supply.  Taps adjoining grease traps or oil separators that could be used for hosing down and cleaning are potential sources of contamination.  Farmers filling spray tanks from taps could contaminate the water source if there is a syphon affect from the tank.  Plumbers with backflow accreditation are trained to assess the risks of contamination and are able to advise on the appropriate device to prevent contamination.

What type of properties may have a testable backflow prevention device installed?

Examples of properties requiring backflow prevention:

  • Hotels, motels and caravan parks
  • Vehicle repair workshops
  • Shops
  • Restaurants
  • Medical and dental surgeries
  • Car and plant washing facilities
  • Dry cleaners and laundries
  • Hospitals and funeral parlours
  • Club houses for sports
  • Schools
  • Day care centres and kindergartens
  • Pest control
  • Water carrying vehicles
  • Banana packing sheds
  • Poison bay filling points
  • Properties with a fire hose reel

Typically domestic premises are considered low risk sources of backflow contamination.  Even so, there are still numerous backflow devices in domestic premises but typically the devices are non-testable and don’t have to be registered with Council.

Types of backflow prevention devices

Types of devices can include:

  • Reduced pressure zone
  • Double check
  • Single check
  • Dual check.

The type of device fitted will depend on the level of potential risk. For example, businesses that produce highly contaminated water as a by-product of their activities will require more complex and reliable devices.

The devices can generally be categorised in two ways: testable and not testable. Reduced pressure zone, double check, and some single check valves are testable devices.   Testable devices can be recognised as they have testing ports or nipples on the valve.  Refer photos.

All testable backflow prevention devices must be registered with Council and must be tested annually by a licenced plumber with backflow accreditation. The results then need to be forwarded to Council. Non-testable devices do not need to be registered or tested annually.

What is Council’s responsibilities?

All local governments in Queensland are required under state legislation (Plumbing and Drainage Regulation 2019 Section 101) to maintain a program for the registration of each testable backflow device in its region and for the monitoring the maintenance and testing of such devices.

What are my responsibilities?

Property owners are required under state legislation to arrange for testable backflow devices to be registered with the local government and ensure the devices are checked, tested and maintained at least once per year by licenced plumber with backflow accreditation.


How do I get my devices registered and tested?  What costs can I expect?

Please contact your preferred plumber to find out if they are backflow accredited.  Accredited plumbers will be able to inspect and test your testable backflow devices and send registration details to Council.  The backflow device must be fully functional to be registered and in some instances maintenance of the device may be required.

 Your plumber should be able to give you a cost to inspect and test your backflow devices.  If repairs are required to the device, your plumber will advise cost implications. The cost of repairing and replacing backflow devices is highly variable and depends on the size and complexity of the valve.  In most instances, spare parts are available for repairs to failing devices.

Is there a fee for registering my device with Council?

There are no fees to register your device with Council during the two year amnesty period. 

When is the amnesty period applicable?

The amnesty period is running until February 2023.

What are other Councils doing?

All Councils are required by legislation to keep a register of backflow prevention devices. Cassowary Coast Council is completing this in line with actions undertaken by other Councils within Queensland.

Can I just have the device removed?

Backflow prevention devices are installed where there is a risk of contaminants entering the potable water supply. As long as the risk exists the device is required to be in place and operational. You may contact a licensed plumber to determine if the device is still required.

What if I choose not to register my testable backflow devices in the amnesty period?

State legislation (Plumbing and Drainage Regulation 2019 Section 102) allows for substantial fines if owners do not meet their mandated backflow prevention requirements.  Council has an obligation to all water consumers to ensure owners with testable backflow prevention devices are complying with Council’s policy and legislation and the imposition of fines may be necessary. 

Where do I go for more information?

Council’s website has some additional information in relation to the adopted Backflow Prevention Policy and Backflow Prevention Management Plan.  If you have further queries in relation to backflow prevention for your property, please contact 1300 763 903 or by emailing

An application to install a testable backflow prevention device needs to be made to Council's Building Department.  A Form 4 needs to be submitted to Council for all valve replacements.

Businesses will receive an annual reminder letter for compliance. Failure to comply will attract a penalty of up to 20 penalty points.

Backflow Prevention Factsheet (this information in a downloadable format)

Backflow Prevention Policy

Backflow Prevention Management Plan