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Plumbing System Solutions – A Guide to Backflow Testing

To understand what backflow testing is, first you need to understand the term backflow. In simple terms, backflow occurs when water flows away from a building rather than towards it. Your drinking water comes to you via pressurised water pipes but if something happens such as a water mains break, high demand at a fire hydrant, or simply reduced water pressure, the water will flow backwards. Unfortunately, this can often cause contamination in your drinking water.

In addition, if your house has an irrigation system, a fire suppression system, or a large boiler, you may also be susceptible to backflow problems. Pesticides could enter your irrigation system or water can become stagnant, also allowing in contaminants into the water you use and consume in your home. Backflow testing helps to prevent your water from contaminants and keep it safe for consumption.

Continue reading to learn more about backflow testing and why it is important to install a backflow prevention device in your home.

What is a Backflow Device?

There are three main backflow prevention devices available and choosing the appropriate device will be dependent on the hazard rating of your property, The type of plumbing system you have and how large, as well as water usage, any building codes that might come into play and also where the device will be installed, also need to be considered. Not everybody is required to have one, however, if you do have something like a suppression system, irrigation system or large boiler, it is mandatory.

An RPZ (Reduced Pressure Zone) device consists of two independent-action, non-return valves which are force-loaded into a closed position. They feature a relief valve which is situated between the two non-return valves. This backflow device is suitable for installation in properties with a high-hazard rating. In this situation, you may also choose to install a Break Tank or Air Gap device, which has an air break between the lowest water service pipe and the upstream tank or container.

For properties with a medium hazard rating, a Testable Double Check Valve can be installed. These devices feature two independent-action, non-return valves which as force-loaded into a closed position. These devices also feature three test taps so that an annual inspection can be conducted.

Who Can Fit A Backflow Device?

In Australia, it is necessary for a licenced plumber with the appropriate backflow prevention accreditation to install, inspect or test backflow devices. Reports can be completed by qualified plumbers and submitted to the necessary organisations.

When Should A Backflow Prevention Device Be Installed?

Backflow devices should be risk assessed on new developments, redevelopments, changes to the existing water supply, and anything that involves the fire service. Backflow risk ratings range from low to high. If it’s low there’s very little risk to health, if it’s medium, it could endanger health, and if it’s high it could even lead to death.

The Importance of Annual Backflow Testing

Every one of the internal components of a backflow prevention device, including valves and springs, needs to be tested on an annual basis. The test involves pressurising the whole unit, after which each part is isolated to make sure it is working correctly. The check valves need to be able to hold a minimum pressure, while the relief valves have to open before a certain pressure is reached.


To ensure that your water supply is safe, you must have these inspections carried out on an annual basis. If the unit does not pass, repairs have to be made to ensure that is brought up to the necessary requirements. Like anything, backflow prevention devices can wear out and have to be repaired or replaced to ensure that they provide the service they are designed for.