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Series SCV Service Check Valves are used in heating applications between boiler piping and system components to facilitate the servicing of components under pressure, such as thermal expansion tanks and float vents, without draining the piping. As the component is threaded into the Service Check Valve, the spring loaded valve opens to system pressure. As the component is removed, the valve closes, maintaining system integrity while the component is being inspected. Series SCV is not to be used on safety relief valves or other safety or flow sensitive components.