Abstract: A method of and apparatus for flushing a water closet by utilizing water and air for the flushing. The method operates at predetermined pressure ratios. At an air pressure of maximally about 3 bar inside of a pressure vessel the flushing medium consisting of air/water is fed into the pressure vessel, and if the pressure exceeds 3 bar, water only is fed into the pressure vessel. In order to feed water and air a water-jet injection is used which on the one hand communicates via an infeed line with the water mains and on the other hand communicates via an infeed stub at the suction side with the ambient air. The air/water mixture is fed through an infeed line into the pressure vessel, which infeed line ends in a space of the pressure vessel which is occupied by an air cushion. The relative pressures allows a two step flushing which is governed by an accordingly designed discharge valve in the outflow conduit of the pressure vessel.