Solder these valves to copper tubing for a permanent, leak-tight connection. They have two integral check valves with a vent between them for maximum protection from system contamination. If the primary check valve fails to close when flow stops or reverses, overflow is discharged through the threaded vent and the secondary check valve prevents backflow. Attach the vent to drain pipes to prevent spillage. These valves are designed for applications with continuous flow and are commonly used on water supply lines to boilers, processing tanks, and other equipment. All have an integral strainer to prevent debris from blocking the check valves.