Abstract: A filling apparatus operating by counterpressure and intended for use on bottling or filling machines for a barrel 1 equipped with an electric sensor 2 for controlling the fill level of the containers, and connected to a solenoid valve E and supply tank B filled with liquid under gaseous pressure, as well as to a detector P that senses the proximity of the container C to be filled. Barrel 1 of filling apparatus A contains a chamber 11 which, when no container C is being applied against the filling apparatus, is divided by two flexible membranes 5, 6-72 into three successive annular chambers 69, 70, 71 separated by the dividing walls 58, 62-621 of the two membranes 5, 6-72.