How a Backflow Prevention Device Works

The necessity of backflow testing and prevention services

In this article we will look at what backflow is, how a backflow prevention device works, the different types available and why you should test your system regularly.

Firstly, let’s look at what backflow is. Backflow is the name given to the flow of unwanted water in a plumbing system, going in the wrong direction. This water is usually contaminated and can cause serious health concerns if it mixes with your normal drinking water. This is why your backflow prevention device is so important.


How it Works

A simple explanation of a backflow prevention device is that it fits onto a pipe and ensures that the water only flows in one direction. This allows clean water to reach your tank but stops the contaminated water from flowing back in the wrong direction.

The system keeps your water clean and safe to drink. If this device fails, it dumps water and the risk of your clean water mixing with the dirty water is much higher. Water dumping can also cause flooding if your device is located indoors. That’s why it’s so important to have it tested on a regular basis.


Types of Backflow Prevention Devices

There are many different types of backflow prevention devices available. The most popular are:

  • Pressure Vacuum Breaker (PVB): These are found in most homes, they are inexpensive, designed simply and easy to install and repair.
  • Double Check Valves (DCA): Installed underground or inside the building, it consists of two independently operating valves, so you have double the protection.
  • Reduced Pressure Zone (RPZ): This is a complex system that offers the most protection. It’s installed underground and you can choose between “inline” or “straight” configuration.

Another type is the atmospheric vacuum breaker (AVB). Each type was designed for a specific function and they provide varying levels of protection. Places such as hospitals and factories work with hazardous waste, so they need a much higher level of protection.


Why Testing is so Important

If the backflow prevention device fails, then your drinking water could become contaminated. The contaminants are rarely visible to the naked eye and drinking it could make you very sick. If you drink impure water it can cause gastrointestinal illnesses, diarrhea, vomiting and stomach cramps. A water filter is not enough protection to keep your water free from impurities.

Testing should be carried out by a professional mechanical plumber on a regular basis. A certified plumber will test the pressure in the system using a testing kit. If the pressure is incorrect that signifies that there could be a problem with the device. Any visible leaks will also indicate there is a problem.

The next step is to take a sample of the water and test it for impurities. The test could save you and other building occupants from drinking dangerous water.

One reason a backflow prevention device may fail could include a faulty valve that causes the system to lose pressure.


What Is The Difference Between a Backflow Preventer and a Check Valve?

A check valve is your first line of defence when it comes to keeping your water clean and drinkable. It’s connected to the backflow prevention device. These components work together to stop water from flowing in the wrong direction and contaminating your drinking water. Check valves need to be fitted in order to protect pumps, filters and sprinkler systems to name a few examples.

A check valve operates automatically and has a back-up in place, so it works even if the power goes out. It can’t be switched to operate manually. They are flow sensitive. The running water keeps the valve open and the water flowing in the right direction.

Not having this device in place can be very dangerous due to cross-contamination.

Do you understand your plumbing system and backflow prevention device better? It’s important to test it regularly—at least every 12 months—and keep it in working order. We can help you with that!

Contact one of our highly skilled Williamstown plumber professionals on 03 9397 1111 or pop us an email on for more information or to book a test. We will analyse and confirm your risk rating and identify any problems. If there is a problem with your device, we will be happy to help you sort out the problem.