line 22 can be minimized the impulses generated by the valve arrangement are substantially absorbed by the flexible spring washer 26 and the flexible web 28 and not transmitted to the exhaust line 22 the web 28 may be provided or perforated with a plurality of openings running in the radial direction the openings advantageously have a diameter of 2 4 mm and are arranged offset or at irregular intervals to one another in the web 28 by means of a web which is provided with openings the transmission of heat from the web 28 to the spring washer 26 and thus to the valve housing 24 is reduced furthermore a perforated web 28 offers the advantage that the noise emission from the web 28 is reduced impulses are generated by the switching of the valve which impulses are transmitted via the web 28 to the exhaust line 22 in the case of a perforated web 28 the propagation of the sound waves in the web 28 is retarded because said sound waves must propagate around the openings and are thus attenuated furthermore the holes arranged in the web yield a better outflow of liquid in particular water which can enter into the valve arrangement from the surroundings since liquid usually enters the valve arrangement from the top it collects between the housing and the web in the case.