Abstract: A ram valve is connected in the supply line through which water flows at a high mass flow rate. A branch line branches off upstream of the valve and includes a check valve and a pressure vessel upstream of the check valve. The ram valve is constructed to have an elongated valve housing and a movable valve body therein, slidable axially in the direction of flow, and shaped to provide for smooth fluid flow therethrough when open and forming a smoothly continuous decreasing flow cross-sectional area. The valve body is held open by an adjustable force, such as a spring or a magnet. When the force is exceeded, the valve body closes suddenly, causing a pressure pulse to be transmitted through the then open check valve into the branch pressure vessel to build up pressure therein. A closed supply pressure vessel having an air cushion is included in the inlet supply line to the valve.