Dual Check Valve with Intermediate Atmospheric Vent Backflow Prevention Device – Backflow Condition – First Check Valve Not Drip Tight

As water is flowing through the DCVwIV, the check valves are open and the intermediate atmospheric vent is closed. If a backflow condition were to occur, the first and second check valve springs would force the check valves to seal against the check valve seat closing both check valves. In a backpressure condition, the intermediate atmospheric vent would be closed since water pressure continues to push against the diaphragm that closes intermediate atmospheric vent. In a backsiphonage condition, the intermediate atmospheric vent is open since there is no water pressure pushing against the diaphragm that closes the intermediate atmospheric vent.

If the first check valve were not operating properly or fouled open during a backsiphonage condition, the closing of the second check valve and the opening of the intermediate atmospheric vent would provide protection. The intermediate atmospheric vent will open because there is no water pressure pushing against the diaphragm that closes the intermediate atmospheric vent. During a backsiphonage condition with the first check valve fouled open, the DCVwIV is still providing protection because the second check valve is holding tight and the intermediate atmospheric vent is open allowing air to enter the area between the check valves, breaking the vacuum and eliminating the siphoning of non-potable water into the potable water system

If the first check valve were not operating properly or fouled open during the backpressure condition, the closing of the second check valve would provide protection. The intermediate atmospheric vent will remain closed since there is still water pressure pushing against the diaphragm that closes the intermediate atmospheric vent. During a backpressure condition with the first check valve fouled open, the DCVwIV is still providing protection because the second check valve is holding tight not allowing non-potable water to enter the potable water system.