What is a backflow prevention device?

A backflow prevention device is a one-way valve (or assembly of valves) installed in a plumbing system to stop water from reversing its normal flow and contaminating the main water supply. When pressure drops in the mains line, water can flow backward from outlets, fixtures, or connected appliances into the public supply. Without protection, contaminated water from pools, garden hoses, chemical tanks, or wastewater can enter drinking water pipes.

In Perth properties, backflow prevention devices are typically fitted at the water meter or at the boundary where the mains connection enters the property. They may also be installed at individual fixtures or appliances that pose contamination risks, such as garden taps, pool fills, or irrigation systems. Local water authorities in Perth require these devices on many properties to meet plumbing codes and protect public water quality.

The devices work by allowing water to flow forward under normal pressure but sealing automatically when reverse flow occurs. Common types include spring-loaded check valves, double check valves, and reduced pressure zone (RPZ) assemblies, each suited to different contamination hazards. An experienced plumber can assess your property's needs and install the appropriate device to meet Perth's water safety standards.