Non-Return Valves are essential to use with self-priming pumps, for suction lifting and for use with pressure switches. They hold the prime in the pump to avoid having to re-prime for every use and to avoid cavitation (dry running) in the pump.
We would also recommend putting a non-return valve on the outlet of a well pump or borehole pump.
A Foot-Valve and Strainer is a non-return valve that is designed to be put on the end of a hose to suction lift out of tanks, rivers and lakes. The strainer stops any debris from finding its way into the pump and the non-return valve will then keep the prime in the hose as well making it easy to transfer from job to job.