A valve body includes a base section having an inlet and an outlet and means forming a valve seat therebetween. A flexible diaphragm is supported for movement relative to the valve seat and includes a center by-pass port which is opened and closed by a valve member supported for axial movement by a closure section of the valve body. A needle-like actuating lever is pivotally supported by a flexible seal secured to the closure section and has an inner end portion projecting into an opening formed within the valve member. An elongated bimetallic actuating element has spaced leg portions mounted on the closure section of the valve body and includes a cantilevered head portion having an opening which receives the outer end portion of the actuating lever. A spring is compressed against the outer end of the actuating lever and causes an over-center rapid toggle action of the lever in response to slower movement of the head portion of the bimetallic actuating element which is preferably connected as a resistance in series with an electrical load. In a modification, the bimetallic actuating element is located within a cup which is formed as a part of the valve body and is positioned to receive an overflow of water from a tank which is supplied with water through the valve. The valve body is supported by an internally threaded tubular fitting having a flange with peripheral teeth for engaging a support bracket and providing for angular adjustment relative to the bracket.