A Reduced Pressure Zone Devic (RPZD, RPZ or RPZ valve) is a type of back-flow prevention device used to protect water supplies from contamination.
A RPZD is considered suitable for significant hazard applications, that is, where the consequence of back-flow 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 back-flow and back-siphonage, because of a redundant design, and because they are testable to verify correct operation.
RPZD are often chosen instead of an air gap since the head loss across the RPZ is much smaller.
A reduced pressure zone device is tested with a device called a differential gauge. This gauge uses hoses attached to the various test cocks of the RPZ and checks to be certain that the check valve springs as well as the relief valve spring are not fouled and are working properly.
RPZ devices are required by law to be tested by a certified control device inspector. Our licensed plumbers are certified to test both residential and commercial properties.