The valve includes a valve seat and a valve body with a circular diaphragm. The valve body is arranged over the valve seat in order to close the latter sealingly when it bears on the valve seat. The valve seat and the valve body have openings which are offset relative to one another and which form a free passage when the diaphragm of the valve body lifts. The diaphragm of the valve body has elongate openings which are uniformly distributed along a circle in the periphery of the diaphragm, the circle having approximately the same center point as the diaphragm. The elongate openings are separated from one another by webs, the diaphragm being designed to be weaker in the area adjacent to these webs.
