receives a socket forming isolation member or tube 38 sealed with the body by an o ring 40 the isolation tube 38 projects beyond the inward end 42 of the body and is sealed fluid tight for the purposes believed apparent the isolation tube 38 loosely receives an elongated flapper lever 44 fig1 having a flapper permanent magnet 46 axially secured in its end portion adjacent the inner closed end of the isolation tube and is connected at its other end with a flapper pivot bushing 48 in turn secured to a flapper pivot shaft 50 horizontally journalled by a pivot support bracket 52 secured to the outer end surface 54 of the body 24 for vertical pivoting movement of the magnet contained end portion of the flapper lever within the confines of the isolation tube the flapper lever 44 operates flapper means 55 for the purpose presently apparent the float means 30 comprises a ball like float 56 threadedly connected with a hollow float magnet holder 58 having a float permanent magnet 60 axially disposed therein fig1 the float magnet holder 58 is supported by the bight portion of a u shaped float arm 62 having legs 64 which are.