around the opening 35 by the application of pressure to the diaphragm as hereinafter to be described the pump body part 31 is provided with an outlet opening 37 in which a ball seat insert 37 made of polypropylene maintained by engagement of a rib 38 formed thereon in a groove 39 a valve member 40 in the form of a ball is provided which is movable into sealing engagement with a seat 41 provided on the insert 37 the ball 40 is maintained in position by a housing 42 provided with an outlet pipe 43 which is connected to a flush pipe 44 of the sanitary pan 8 the pump body part 31 is provided with a generally cylindrical portion 50 to which is clamped by a clamp ring 51 a flexible bellows 52 made of p v c the bellows 52 is of generally cylindrical configuration having a generally cylindrical wall 53 of corrugated configuration to provide a collapsible bellows and a closed top wall 54 which is connected to a plate 55 from which an operating rod or link 56 extends vertically upwardly through an opening 57 in the top wall 26 of the receptacle 20 the top wall 26 is provided with a bearing 58 to guide the rod 56 for vertical sliding movement the bellows 52 provides a majority of variable volume pumping chamber the remainder of which is defined by the pump body part 31 a coil compression spring 59 encircles the rod 56 and is engaged between the plate 26 and foot pedal 10.