Bronze Vented Loop - 3/4 Hose Features:Allows air to enter to break siphon, but does not permit air and odors to escape! Cap is threaded 1/2 NPT to accept a barb fitting if you wish to vent overboard.Overboard venting is required if PVL or HVL series is used in an exhaust system.HVL and PVL series vented loops assure clog-free anti-siphon protection for sanitation or engine exhaust systems. The oversized vent valve can easily be removed for inspection or cleaning without tools.Mount Hardware is included.