Reduced pressure detector assembly is an outgrowth of the double check detector assembly and is typically used on fire line applications. This assembly is intended to protect the potable water supply from fire sprinkler systems that contain chemical additives or can be connected to an auxiliary non-potable water source. This assembly is comprised of a mainline reduced pressure backflow assembly equipped with OS&Y gate valves, a bypass arrangement containing a smaller reduced pressure backflow assembly and water meter.

Reduced pressure zone assembly consists of two independently operating, spring loaded cam-check valves with a hydraulically operated differential pressure relief valve located between and below the cam-checks, required test cocks and optional inlet and outlet resilient seat shutoff valves. When normal flow exists, both checks, called the zone, is at least 2 PSI lower than the inlet pressure. The differential pressure relief valve is closed during the normal flow. The cam-checks include a stainless steel spring and cam-arm, rubber faced disc and a replaceable seat. It is used to protect against high hazard (toxic) fluids in water services to industrial plants, hospitals, morgues, mortuaries, and chemical plants.