is mounted a permanent magnet 30 the remaining portion of the float 53 is filled with foam material or air 35 the float can move up and down in the float chamber 50 as liquid enters slot 34 in the enclosure 32 as the float 53 moves upward in the float chamber 50 air in the float chamber 50 passes out a one way valve 62 mounted on the top end 61 of the float chamber 50 an opening 60 allows the air to escape through the side wall of a protective cover member 63 above the one way valve 62 the switch chamber 31 is liquid tight sealed and separated by partition walls 36 37 and 51 from the float chamber 50 and an ultrasonic sealed cover 65 in the switch chamber 31 supports a reed type switch 41 which has normally opened contacts 42 and 43 and that are closed when the float 53 moves sufficiently upwardly in the float chamber 50 so that the magnet 30 can close the contacts 42 and 43 in u s pat no 5 297 939 the float valve and switch housing was connected to the housing of the pump 11 and the present invention is applicable to the structure of u s pat no 5 297 939 or the structure of.