RPZ in a Flow or Dynamic State – Relief Valve Closed
As water is introduced into the device, it enters the relief valve high-pressure area located on the upstream side of the diaphragm that separates the relief valve high-pressure area from the low-pressure area. The high-pressure water (supply pressure) enters the relief valve high-pressure area through the sensing line, which is connected to the supply side of the device. The sensing line is upstream of the first check valve and downstream of the upstream shut-off valve between test cock number one and two. The high water pressure exerts a force against the diaphragm compresses the relief valve spring causing the relief valve to close. The relief valve is designed to keep the water pressure in the zone between the first and second check valves at a minimum of 2 PSI less than the supply pressure.