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Installing a Big Mouth vent - question about height

I'm replacing a very old Maid-O-Mist main vent with a B&J Big Mouth. The old vent sat directly on my return pipe and this new vent will fit fine like that but I've read that it should ideally be installed about 6 (?) inches above the return pipe. Is that right? Unfortunately I have a gas pipe and floor joist right above the tap. Has anyone installed it directly into return without any problems? If not, can I put an elbow on there and divert it 4 inches to the side or will that cause any problems (like a bottleneck)?



  • IronmanIronman Posts: 5,417Member
    Just Ell it over and up as much as you reasonably can.

    What's ideal, and what can actually be done in the field, are often two different things.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Jamie HallJamie Hall Posts: 11,889Member
    Do the elbow thing. It will work just fine.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Dan_NJDan_NJ Posts: 117Member
    I had a similar deal, ring main with vent right by the dry return. I used a 1/2 " street 90 in the main > nipple > 90 elbow > Bigmouth. Set the nipple so it points uphill for drainage. Works like a champ, especially now that the pressure is staying under 2 psi.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 6,312Member
    Yes, elbow over but if possible use 2 45s instead of 90s
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