Abstract: An automatically acting switch valve for a combined water meter which has a main meter for measuring larger flows and a secondary meter for measuring smaller flows. The switch valve has a switch insert including a carrier with a central slide bolt fastened to it, a shut-off member displaceably guided on the bolt and urged into closed position by a spring, a sealing seat of greatly narrowed cross section provided with an elastic seal between the carrier and the shut-off member. An annular chamber receives the shut-off member and opens downstream. It has a cylindrical zone and an adjoining same a conically narrowing annular zone which terminates in a narrowed shut-off member retention step. The shut-off member has a disk-shaped rim the front part of which is contained, in the closed position of the valve, within the cylindrical zone of the annular chamber.