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Thread: Roof venting

  1. #1
    Join Date
    Mar 2010

    Talking Roof venting

    I am reworking my plumbing to a small bedroom ;changing it into a full bath. I am running a 3" vent thru the roof. Can i tie all the other vents into this one 3" vent before it exits the roof. All the revents will be on a 1/4" per foot grade to where they would tie into the 3" line before it exits the roof. Reason is so there won't be so many pipes protruding. Is this ok with plumbing code, thanks?

  2. #2
    Join Date
    Jan 2010

    Default Re: Roof venting

    Almost certainly it's OK.

    No doubt at all if you are on the International Plumbing Code; if you're on the Uniform Plumbing Code, it's OK unless: 1) There are more than 3 toilets in the house, and, 2) The 3" vent is the only vent thru the roof.

    The UPC requires that the total cross-sectional area of the roof vents must be at least as much as the cross-sectional area of the required size of the building drain--having more than 3 toilets would mean that the building drain would have to be 4".

  3. #3
    Join Date
    Aug 2007
    The Great White North

    Default Re: Roof venting

    Yep -- agreed --- it's fine.

    regarding the 1/4 inch slope it's not required for the vent --- that's more for the drain portion.
    However, something I learned a very long time ago from a master plumber was having the vent branches sloped in the attic. As he described , even though it's just for air there is a certain amount of moisture from condensation and/or rain that can become trapped in horizontal runs within the attic. By having the vent branches sloped down from the stack --- or up to the stack , depending how you look at it --- allows that accumulated moisture to drain out.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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