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MF 840 Vented Loop, 1-1/2" (White)
Vented Loops are commonly used in marine toilet, bilge, and engine cooling systems. The simple inverted duckbill valve system incorporated in the top of the loop allows air to enter the line when not in use, yet effectively seals as water or other fluid passes through.
Molded in glass-reinforced Marelon, neither vent nor loop will corrode. The duckbill one way valve is designed to seal properly, even if particulate matter is present in fluids.
The available MF-846 vent barb assembly option can be used in lieu of the standard MF-841 cap and duckbill. This option allows valveless venting - without the liabilities of a duckbill possibly fouling. Venting can be to the outside of the hull via a 1/4"(6.35mm) hose, or simply running the hose vertically toward the overhead, above any possible water level.
Forespar has produced a 3-1/2 minute video covering the safety advantages of vented loops, as well as several tips about mounting and maintenance.