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Backflow prevention protects your drinking water from contamination by stopping water from flowing backwards through your plumbing system. Here's what every property owner needs to know about backflow risks and prevention requirements.
What Is Backflow?
Backflow occurs when water flows in the opposite direction to its intended path through your plumbing system. Instead of clean water flowing from the mains supply into your home, contaminated water can be drawn backwards into the drinking water supply.
This typically happens due to one of two conditions:
- Back-siphonage: A sudden drop in mains water pressure (for example, during a water main break or when fire hydrants are in use) creates a vacuum that sucks water backwards through the system
- Back-pressure: Pressure in your private plumbing system exceeds the mains supply pressure, forcing water backwards. This can occur with booster pumps, elevated tanks, or thermal expansion in hot water systems
Why Is It Dangerous?
Backflow can allow contaminated water from gardens (with fertiliser and pesticides), swimming pools (with chlorine and chemicals), commercial processes, or even sewage to enter the drinking water supply. This poses serious health risks including exposure to bacteria, chemicals, and other harmful substances.
In Australia, there have been documented cases of backflow causing illness in entire neighbourhoods when contaminated water from one property entered the shared mains supply.
Backflow Prevention Devices
Backflow prevention devices are mechanical valves that allow water to flow in one direction only. The type of device required depends on the level of risk at your property:
Hose connection vacuum breakers: The simplest device, fitted to outdoor garden taps. Prevents back-siphonage from garden hoses that may be lying in pools of water or near chemical containers.
Dual check valves: Installed at the water meter for low-risk residential properties. These are non-testable devices that provide basic protection.
Reduced pressure zone (RPZ) devices: The highest level of protection, required for high-risk properties such as commercial premises, properties with irrigation systems connected to chemical injection, or any connection that poses a severe contamination risk. RPZ valves must be tested annually by a licensed plumber.
Testable double check valves: Used for medium-risk applications. Like RPZ devices, these must be tested annually.
Who Needs Backflow Prevention?
Under Australian Standards (AS 3500.1) and local council regulations, backflow prevention is required for:
- All new residential properties (typically a dual check valve at the meter)
- Properties with in-ground irrigation systems
- Commercial and industrial properties
- Properties with swimming pools connected to the mains supply
- Any property identified by the water authority as posing a contamination risk
Annual Testing Requirements
If your property has a testable backflow prevention device (RPZ or testable double check valve), it must be tested annually by a licensed plumber who holds a backflow prevention endorsement. Test results must be submitted to your local water authority.
Failure to maintain and test your backflow device can result in fines and, more importantly, puts the community water supply at risk.
Need a Backflow Test?
Our licensed plumbers hold current backflow prevention endorsements and can test, service, and install all types of backflow prevention devices. We handle the paperwork and submit test results directly to your water authority on your behalf.
