What is the main difference between an RPZ and a double check valve?

The main distinction between a Reduced Pressure Zone (RPZ) assembly and a double check valve lies in the level of protection they offer against backpressure and backsiphonage. An RPZ is specifically designed to prevent backflow due to both backpressure and backsiphonage. This consists of two check valves and a relief valve that maintains a consistent pressure differential, ensuring that if either of the check valves fails, the relief valve will open to discharge contaminants and maintain a safe environment.

In contrast, while a double check valve does provide some level of backflow prevention, it does not have the capability to relieve pressure in the same way that an RPZ does, which makes it less effective in high-risk scenarios where toxic substances or contaminants may be present. Thus, the additional protective feature of the RPZ makes it the preferred choice in applications where there is a noticeable risk for backpressure.