Frequently Asked Questions

Three-port vented pilot-to-open, or atmospherically referenced, check valves are considered problem solvers for existing circuits that used a non-vented valve. If a vented valve is required in a new design, four-port valves are recommended. Atmospherically referenced valves may leak externally and pose a threat for intrusion of moisture (and resulting corrosion) in the spring chamber even though the spring chamber is sealed.