a circular base member 43 resting on the partition 18 and loosely surrounding the plateform portion 181 and a connection arm 55 with one end hingedly attached to bottom end of the vertical post 51 and another end attached to outer side wall of the circular base member 43 a holder 52 attached to an interior of a side wall of the housing 1 and extending therethrough an axial bore not shown in which the vertical post 51 is mounted for rotary motion only the actuating arm 54 is swingable relative to the vertical post 51 between a lower engaging position as best shown in fig1 and an upper disengaging position as best shown in fig3 the actuating arm 54 has a sharp head extending into adjacent teeth of the pinion 21 as best shown in fig2 when the actuating arm 54 is located in its lower engaging position a float 53 is secured to the actuating arm 54 for conducting swinging movement of the actuating arm 54 along with rising or decreasing water level in the water chamber 11 coil springs 46 are arranged between interior of the side wall of the housing 1 and outer side wall of the circular base member 43 to restore automatically the circular base member 43 after the base member 43 being displaced from its ordinary position as best shown in fig1 and 4 a valve retaining device includes a valve retainer 41 which is an annular float loosely surrounding the float valve 3 and normally resting on top of the base member 43 for retaining the float valve 3 in its closed position and magnets 42 45.