When is a backflow prevention device required?
Summary (TL;DR)
Backflow prevention devices are required under AS/NZS 3500.1 whenever there is a risk of contaminated water flowing backwards into the drinking water supply. The type of device required depends on the hazard rating: Low Hazard (non-testable devices), Medium Hazard (testable Double Check valves), or High Hazard (testable RPZ valves).
Backflow Prevention Hazard Ratings
To determine what type of backflow device is required, AS/NZS 3500.1 classifies the risk of contamination into three hazard ratings.
1. Low Hazard
Any condition where the water might be polluted but would not endanger health (e.g., a change in taste, colour, or odour).
- Examples: Standard residential hose taps, residential irrigation systems without chemical injection.
- Required Device: Non-testable devices like a Dual Check Valve (usually integrated into the water meter) or a vacuum breaker on a hose tap.
2. Medium Hazard
Any condition that could endanger health.
- Examples: Commercial kitchens, public swimming pools, residential irrigation systems with chemical injection.
- Required Device: Testable Double Check Valve (DCV). Must be tested annually and a Form 9 lodged.
3. High Hazard
Any condition that could cause death.
- Examples: Hospitals, mortuaries, abattoirs, chemical plants, car washes, cooling towers.
- Required Device: Testable Reduced Pressure Zone (RPZ) device or a registered break tank. Must be tested annually and a Form 9 lodged.
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