A foot valve is a type of check valve that is typically installed at a pump or at the bottom of a pipe line (hence the name). Foot valves act like ball check valves, but have an open end with a shield or screen over it to block debris from entering the line. The valve opening is designed to be larger than the line itself, minimizing head loss.
Foot valves can be found in ponds, pools and almost anywhere there is a pump. These special valves allow the pump to stay primed, letting liquid to flow in, but keeping it from flowing back out. The screens or baskets that cover the valve opening tend to get clogged over time, especially in ponds and wells. It is important to check and clean your valves regularly for optimum performance.