What Is Backflow Prevention?
Backflow prevention refers to the devices, methods, and regulations designed to stop contaminated or polluted water from reversing direction and flowing back into the potable (drinking) water supply. This can happen when water pressure drops suddenly — for example during a water main break or heavy demand — causing a siphon effect that pulls non-potable water into clean supply lines.
How Backflow Prevention Works
Backflow prevention devices are installed at cross-connection points where the potable water supply could come into contact with a potential source of contamination. Common device types include:
- Reduced Pressure Zone (RPZ) valve — highest level of protection, required for high-hazard situations
- Double Check Valve Assembly (DCVA) — used for medium-hazard connections
- Hose Connection Vacuum Breaker — for outdoor taps and irrigation systems
- Air Gap — the simplest form, a physical gap between the water outlet and any potential contamination source
Under AS/NZS 3500 (Plumbing and Drainage), property owners are responsible for ensuring backflow prevention devices are installed, tested annually by a licensed plumber, and registered with their local water authority.
State Variations
| State/Territory | Regulatory Body | Annual Test Required? |
|---|---|---|
| QLD | Local water authority | Yes |
| NSW | Sydney Water / local council | Yes |
| VIC | Local water authority | Yes |
| WA | Water Corporation | Yes |
| SA | SA Water | Yes |
| TAS | TasWater | Yes |
| ACT | Icon Water | Yes |
| NT | Power and Water Corporation | Yes |
How It Relates to Licence Verification
Backflow prevention device installation, testing, and certification must be performed by a licensed plumber who holds the appropriate endorsement. Only licensed professionals can issue compliance certificates for backflow devices. Use TradieVerify to verify your plumber’s licence and ensure they are qualified to work on backflow prevention systems in your state.