The Double Check Valve Device Assembly – Flow or Dynamic State with Backsiphonage First Check Closed Tight and Second Check Valve Fouled Open

During the normal operations of a DCVA, the springs loaded check valves are closed when there is no demand downstream. When there is a demand downstream, the spring loaded check valves will open except when there is a backsiphonage backflow occurrence in the inlet water supply piping system. When this occurs, pressure upstream of the first check valve is sup-atmospheric. Because of the backsiphonage situation in the inlet water piping system, the DCVA is in a static state and the first check valve will close tight, if not fouled or not working properly. If the second check valve is functioning it will hold tight. Pressure upstream of the first check valve is sub-atmospheric and the pressure downstream of the first check valve and upstream of the second check valve is positive. If the second check valve is not holding tight, the water pressure downstream of the first check valve is the same as the pressure downstream of the second check valve and the first check valve is holding back pressurized non-potable water. Since there is negative pressure upstream of the first check valve the spring and positive pressure downstream of the first check valve will close the first check valve. The closed first check valve prevents non-potable from siphoning back into the potable water system. The DCVA is providing protection. The status or condition of the check valves can only be determined at the time that the DCVA is tested.