These spring-operated poppet valves, with optional relief settings, allow free flow in only one direction and prevent backflow – sometimes referred to as “backflow preventor”, “flow stop”, or “non-return” valve. They also are used for relief and by-pass functions; however, they should not be used as safety relief valves. Kepner's Flexible Seal Seat™ combines metal-to-metal contact with a resilient seal seat ensuring dependable bubble-tight shutoff of liquid or gas, and long service life. Standard and specialty valve designs handle a wide variety of applications.

For Commercial Brass F Hex = 2 3/4 inch.