and an outlet 7 a valve disk 2 operates in conjunction with a valve seat 3 to control the flow of water between the inlet and the outlet the valve disk 2 is mounted to a supporting member 9 which is in turn mounted to the rear end of the housing 5 by a set screw 4 the set screw is positioned in a threaded opening within a closure plug 4a the set screw bears against a connecting member 9a and is rotatable with respect thereto an expandable element such as a longitudinally expanding wax filled thermostatic element 1 or the like is mounted to and positioned between members 9 and 9a a coil spring 8 is supported by the disk 2 at one end thereof and an abutment member 8a near the outlet 7 the spring resiliently urges the valve disk 2 away from the valve seat 3 in order to allow the free flow of water between the inlet 6 and outlet 7 under normal conditions should the temperature of the water entering the housing 5 exceed a preselected maximum e g 113 u00b0 f the expandable element 1 will have expanded sufficiently so as to cause the valve disk 2 to enter into the opening within seat.