The foot valve is a lift check valve which is usually installed together with suction strainers in the suction line. It prevents the suction line from running empty after the pump is stopped (also see Valve).
The foot valve should be installed in such a way that an appropriate distance between the valve, the pump sump floor and the lowest suction-side water level is maintained.
A type often used is a cup valve as it features favourable flow characteristics (see Head losses). See Fig. 1 Foot valve