Wet Alarm Check Valves (DN80 to DN250) are used in wet pipe fire sprinkler systems. They primarily serve a dual purpose in which to prevent a reverse flow of water through their bodies (non-return) and also provide for the use of a hydraulic fire alarm, independent upon an electrical power supply for its operation.

Through the use of a hydraulic retard chamber a time delay is provided to eliminate potential false alarms caused by fluctuating water supply pressures, where constant pressure water supplies are used the retard chamber (time delay) is not necessary. By incorporating the use of electrical pressure switches, supplemental alarms, on annunciators, may also be used.