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Reduced Pressure Zone (RPZ)

A Reduced Pressure Zone Device (RPZD, RPZ or RPZ valve) is a type of backflow prevention device used to protect water supplies from contamination. RPZDs may also be known as reduced pressure principle backflow prevention devices, or reduced pressure zone assemblies.

A RPZD is considered suitable for significant hazard applications where the consequence of backflow into the water supply would cause significant harm, although not for the highest risks, such as human waste. They are considered suitable because they prevent both backflow and back-siphonage, because of a redundant design (even with two check valves broken the device still provides protection), and because they are testable to verify correct operation.

Double Check Valve (DCV)

A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination.

Usage in Water Supply: In the case of usage in water supply, it consists of two check valves assembled in series. This employs two operating principles: firstly one check valve will still act, even if the other is jammed wide open. Secondly the closure of one valve reduces the pressure differential across the other, allowing a more reliable seal and avoiding even minor leakage.

Small valves may be so compact as to be barely noticeable, particularly when they are integrated into the bodies of existing taps (faucets). Larger check valves may be installed with ball valves at the ends, for isolation and testing. Often, test cocks (very small ball valves) are in place to attach test equipment for evaluating whether the double check assembly is still functional.

The double check valve assembly is suitable for prevention of back pressure and back siphonage, but is not suitable for high hazard applications. If the hazard is higher, even a relatively low hazard such as using antifreeze in the fire sprinkler system, then a more reliable check valve such as a Reduced pressure zone device may be mandated.

For more information regarding Backflow installation, inspection or repair services please contact our service department at (877) 749.FIRE (3473) or email us at This e-mail address is being protected from spambots. You need JavaScript enabled to view it.