The Double Check Valve Device Assembly (DCVA) – Flow or Dynamic State with Backpressure First and Second Check Valves Holding Tight
During the normal operations of a DCVA the springs loaded check valves are closed when there is no demand downstream. The spring loaded check valves will open when there is a demand downstream except when there is a backpressure backflow occurrence created by a pump, elevated storage tank or due to elevation head or thermal expansion in the piping system. When this occurs, the second check valve will close. Since the DCVA is in static state due to the backpressure, the first and second valves will close. The DCVA is providing protection. If the second check valve was fouled with debris and could not close, the first check would hold tight and the device would still provide protection. If the first check were fouled as well under a backpressure condition, the device would not offer protection.
