44 of the float 40 the magnetically attracting force between the extensions 42 of the float 40 and the blocks 32 of the frame 30 is smaller than the floating force or the buoyancy of the float 40 and is thus not good enough to force the float 40 downwardly to block the outlet pipe 20 at this moment the float 40 may float upwardly away from the outlet pipe 20 fig8 to allow the water in the receptacle 10 to flow out through the outlet pipe 20 and to flush the toilet 12 fig9 it is preferable that the core 56 may be formed into different polarity from that of the magnet 44 when the core 56 is separated from the projections 43 or the magnets 44 of the float 40 or when the core 56 is forced into the duct 55 by the coil 57 in order to further force the magnet 44 and the float 40 upwardly away from the frame 30 and the electromagnetic devices 50 after the water flushing operation the float 40 may move downwardly to block the outlet pipe 20 again the electromagnetic devices 50 may be switched off or de energized when the float 40 floats upwardly away from the outlet pipe 20 to conduct the water flushing operation at this moment the core 56 is not acted by the coil 57 and may be attracted to the magnet 44 to solidly retain the float 40 to the frame 30 and to solidly block the outlet pipe 20 again as shown in fig2 u2013 4 a usual pull chain 45 may further be provided and coupled between the float 40 and the actuating knob 14 fig1 to allow the float 40 to be pulled and.