RPZ Valve vs Double Check Valve
Both are backflow prevention devices, but they offer very different levels of protection. Here is how to tell them apart.
| Feature | RPZ valve | Double check valve |
|---|---|---|
| Number of check valves | Two in series | Two in series |
| Relief valve to atmosphere | Yes | No |
| Discharge under fault | Dumps to atmosphere | None — relies on check valves only |
| Typical fluid category | Up to 3, and 4 where approved | Up to 3 |
| Higher-risk protection | Yes | No |
| Requires annual test | Generally yes | Recommended; check requirements |
| Cost | Higher | Lower |
The key difference is the relief valve. An RPZ valve actively dumps water to atmosphere under fault conditions, giving a much higher level of protection. A double check valve relies only on its two check valves and cannot discharge — so it is not suitable for higher-risk fluids.