Dual Check Valve with Intermediate Atmospheric Vent Backflow Prevention Device – Backflow Condition – First and Second 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 and second check valves were not operating properly or fouled open during the backsiphonage condition, 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 and second check valve fouled open, the DCVwIV is still providing protection because the intermediate atmospheric vent is open allowing air to enterer 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 and second check valves were not operating properly or fouled open during the backpressure condition, the intermediate atmospheric vent may remain closed since there is water pressure pushing against the diaphragm that closes the intermediate atmospheric vent. However, under certain differential pressure conditions between the inlet and outlet pressures, the intermediate atmospheric vent may open during a backpressure condition if the second check valve is fouled open. During a backpressure condition with the first and second check valve fouled open, the DCVwIV may provide protection because the intermediate atmospheric vent may open depending of the differential pressure status. Because of the intermediate atmospheric vent-opening design specifications, the DCVwIV is only suitable for use on low-hazard cross-connections.