The check valves permit flow in one direction only; the operation of the valve is based on the movement of a small disc. The disc shifts within the housing as the pressure differential changes from forward to reverse. A flat surface on one side of the disc seals off flow, while the other side allows flow to pass.
The check valves offer low "cracking pressure" and a minimum differential forward flow, less than 0.005 PSI in the standard units.
