The Double Check Valve Device Assembly (DCVA) – Flow or Dynamic State with Backpressure Second Check Valve Fouled Open and First Holding Tight
During the normal operations of a DCVA, the check valve 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 if not fouled. If the second check valve is fouled open, the high pressure non-potable water will pass back through the second check valve and backpressure the first check valve, closing the first check valve with the assistance of the spring. The DCVA is providing protection since the first check valve is holding tight. The status or condition of the check valves can only be determined at the time that the DCVA is tested.