Check valves permit water flow in one direction only and generally are recommended for all submersible pump installations. Their purpose is to prevent the water in the column above the pump and in the pressure tank from draining back into the well when the pump shuts off. Some submersible pumps have built-in check valves and are suitable for operation without an external check valve, provided the pump setting is not too deep. Consult your pump manufacturer concerning proper application and installation.
Spring loaded, stem or cage poppet style check valves should be used with submersible pumps. They are designed to close quickly as the water flow stops and begins to move in a reverse direction. Swing type check valves should not be used. When tile pump stops, there is a sudden reversal of flow before the swing check closes, causing a sudden change in tile velocity of tile water and a water hammer.