Abstract: A control device including an inlet pipe and an outlet pipe disposed in the water tank, a valve disposed on top of the outlet pipe, a pawl rotatably supported on top of the inlet pipe, a float slidably engaged on the inlet pipe, a pusher extended downward from the float, the float will be caught by the pawl when the float moves downward, the outlet pipe will be closed by the valve after all of the water has been discharged, and the float will not be caught by the pawl when the knob is released right after depression so that the float may move downward to push the valve.