Abstract: In a discharge valve for liquids, and especially for use in lavatories, comprising two bodies provided with hollow spaces separated from each other by a circular diaphragm, the central portion of which normally seals an inlet conduit for water which, jointly with the discharge conduit for water, opens into one of said hollow spaces, while the other one of said hollow spaces is connected by means of respective channels provided with flow restrictors, one to the inlet for water and the other one to the outlet for water, the said channels crossing the peripheral zone of said diaphragm, the following combination of improvements:(a) The channel intercommunicating the hollow spaces opens in the water inlet conduit in such a manner as to proceed upstream;(b) The guide of the piston of the plug sealing the water outlet ends in a projection in the shape of a truncated cone;(c) The sealing diaphragm has a thickening in the shape of a truncated cone; and(d) The zones surrounding the flat contact surfaces between stiff m