The Double Check Valve Device Assembly – Flow or Dynamic State with Backsiphonage First Check Fouled Open and Second Check Valve Holding Tight
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 check valves will close tight if not fouled or not working properly. If the first check valve does not close tight the second check valve, if not fouled, will close tight. If the first check is not holding tight, sub-atmospheric pressure is now upstream of the second check valve. Since there is negative pressure upstream of the second check valve the spring and positive pressure will close the second check valve. The second check valve is holding back pressurized non-potable water. A siphoning situation is prevented. The closed second 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.
