PURPOSE: To stop feeding water when a low tank is filled with water by providing a circuit constitution which continues to feed water until the low tank is filled with water even if a water level sensor operates to turn on.

CONSTITUTION: If the water level drops below a specific level and a water level sensor microswitch D is switched to turn on when water is fed to the low tank while the water level sensor microswitch D is above the specific water level in the storage tank, a partial circuit between the power receptacle nd outlet G of a well pump turns off. The power supply, however, is prevented from being cut through the circuit constitution of a well pump internal float relay contact A extending in parallel to this circuit, so water is fed continuesly. When the low tank is filled with water and a low tank feed water valve is closed to stop the water flow, a float detection sensor is turned off, and consequently a float relay is turned off and a float relay contact A is opened to stop the power supply of an AC outlet G, so that the well pump device stops.