The Principle Operation of a Dual Check Valve with Intermediate Atmospheric Vent – Backflow Prevention Device – Flowing or Dynamic State
As water is introduced into the DCVwIV, the water pressure opens the first check or primary check valve and pushes against the diaphragm seal to close the intermediate atmospheric vent. The intermediate atmospheric vent remains closed by deflection of diaphragm seal. As water continues to flow through the DCVwIV, the water pressure opens the second or secondary check valve opens away from downstream seat, permitting the flow of water to continue through DCVwIV. With water flowing through the DCVwIV, the supply pressure closes the atmospheric vent and both check valves are opened by supply pressure.
