MF 847 Vented Loop - 1-1/8" Installing one of our vented loops will ensure that fluids do not siphon from tank to tank. Vented loops are commonly used in the marine toilet system and engine cooling system. The simple Valve system built into the top of the loop allows air to enter the line when not in use, but seals effectively as water or other liquid passes through. Molded in Marelon, neither the vent nor the loop is will corrode. Duckbill one-way valve is designed to seal properly if particulate matter is present in liquids. Specifications: Barb Size: 1.125 in. Height: 7.000 in. Width: 9.000 in.