The Principle Operation of a Dual Check Valve Backflow Prevention Device – Flowing or Dynamic State
As water flows through the DuCV, the inlet or supply pressure opens the first spring loaded check valve. As water fills the area between the check valves, the water pressure opens the second spring loaded check valve. Since, the check valves are spring loaded a pressure loss is created across the first and second check valve. The force of the check valve springs is trying to keep the check valves in a closed position. As water continues to flow through the DuCV due to a downstream demand, a differential pressure across the DuCV is created by the tensile strength of the springs and friction.