News & Updates

What is Backflow Prevention?

Backflow Prevention Systems are vital to conserving the cleanliness of our water supply!

The water in your everyday plumbing typically flows in one direction. From a potable supply through the fixtures in your building, such as faucets and showers, down the drain and to the sewer system. Adequate water pressure usually maintains this flow. This is so that you can turn on your faucet and enjoy a safe and refreshing drink.

However, if the pressure in the water main goes lower than the pressure in your plumbing supply, backflow can occur. The flow changes direction and may cause waste, pollutants and other hazardous materials to enter into your water supply. Your life-giving liquid then presents a hazard to your health. Changes in pressure can happen if the water main bursts or there’s a high demand, such as during fire fighting operations.


A simple way to prevent backflow is to add an air gap. This is a vertical space between where the water comes from, such as a valve, and where water can collect, such as a sink. In more complex systems or when there’s a greater risk of contaminants entering the water supply. A physical backflow prevention device is needed at each connection to the drinking water supply. Specific situations also require the device:

  • New construction
  • Additions to or redevelopment of existing facilities
  • Changes to water service
  • Multiple buildings, whether residential or commercial
  • Fire service applications, including new services that require a medium-rated device. No devices are needed for existing fire services, unless they are being modified
  • Ornamental or recreational bodies of water, such as swimming pools, fish ponds, or fountains. The backflow risk for such installations needs to be investigated to determine if they need prevention devices


The Water Services Act 2012 and Water Services Regulations 2013 mandate the installation of backflow prevention devices. This is to protect the public from the health problems or death caused by backflow incidents. You may receive notice to install these devices at plumbing connections within your property boundary. If you do not comply, you may be fined up to $5,000 plus $500 per day, or have your water services restricted or disconnected.

Backflow prevention devices can only a licensed plumbing contractor. The contractor installs the device inside your property boundary on your side of the water connection. The device must be out in the open. It cannot be put in a pit, chamber, or underground. After installation, the contractor must register the device.


Several backflow devices are available:

  • The Atmospheric Vacuum Breaker – Inexpensive, consisting of an inlet valve, check seat, and an air inlet port. This protects against backsiphonage, which is caused by negative pressure in the pipes. This device does not protect against back pressure. Back pressure occurs when water pressure later in the flow is greater than from the water supply.
  • The Pressure Vacuum Breaker. Contains internally loaded check and loaded air inlet valves and can be tested. It protects against backsiphonage but not back pressure.
  • The Double Check Valve. Contains two independent resilient seat-check valves. These are between two shut-off valves as well as test cocks and stop valves for testing.
  • The Reduced-Pressure Principle Backflow-Preventer. Made up of an automatic differential-pressure valve between two or more independent resilient seat-check valves.
  • These are also between shut-off valves. Test cocks provide for checking.
  • The Hose Bibb Vacuum Breaker. Prevents backsiphonage on faucets but is prone to back pressure if the hose outlet is higher than the s.


Depending on how your land is used, the type of device that you need will be defined by the backflow risk of your property;

  • Low Risk: Problems with the connection to the drinking water supply may be a nuisance but do not endanger health or causes injury.
  • Medium Risk: Problems could endanger health
  • High Risk: Problems could cause death.

Your property receives a risk rating when the building application is approved. Descriptions in the Land Use Code are used for assigning the risk level, based on what you plan on doing in the property. For example, if your property is either used for industrial waste process or has unknown uses, it receives a high-risk rating. Your plumbing contractor can advise you on the minimum type of backflow device needed in your system based on the rating.


You are responsible for maintaining the backflow prevention devices on your property since you own them. Testable devices require checking at commissioning, after maintenance or at least annually. Only licensed plumbing contractors may test these devices. They must give you the results within five days after the test. Otherwise, there’s a penalty of $1,000. If you do not maintain the devices, you may receive a non-compliance notice.

Backflow prevention devices are necessary to keep you and the other occupants of your property safe and healthy. Don’t avoid their installation just to save money or because it’s inconvenient. You risk the health and safety of people as well as expose yourself to fines and disconnection of water service.

Contact us to learn about our Backflow Prevention services in Perth.



commercial plumber - PBR Plumbing