Abstract: In a filtration apparatus of the type wherein the material to be filtered is fed to an inner compartment between a filter element, supported by a hollow perforated cylindrical body, and a concentric flexible bladder, the bladder being capable of being pressed by a hydraulic fluid against the material to be filtered thus forcing the liquid component through the filter, the inlet to the inner compartment for liquid/solid mixtures comprises a substantially cylindrical chamber provided with circumferentially-spaced apertures adapted to connect with the inner compartment, said chamber being located at one end of the cylindrical body, an inlet line or lines into said chamber and a hollow cylindrical member movably constructed and arranged to cover or expose said apertures.