Connecting dwv vents in attic

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Finishguy007, Mar 15, 2013.

  1. Finishguy007

    Finishguy007 New Member

    Messages:
    4
    Location:
    Pgh Pa
    1 shower, 2 sinks, 1 whirlpool tub and 1 toilet. Can all these vents connect in the attic and return to the main 3" vent stack? Distance they must travel in attic is 25' approx.
  2. Terry

    Terry Administrator Staff Member

    Messages:
    14,754
    Location:
    Bothell, Washington
    Yes.

    If the horizontal is more than 1/3 the vertical, you go up one pipe size.
  3. Finishguy007

    Finishguy007 New Member

    Messages:
    4
    Location:
    Pgh Pa
    If the horizontal run is 1/3 the vertical rise. Is that what you mean?
  4. Terry

    Terry Administrator Staff Member

    Messages:
    14,754
    Location:
    Bothell, Washington
    More than. It can be up to 1/3 the vertical. If more than that, it bumps a size. That keeps the inspector happy.
    That hardly ever comes into play.
  5. Finishguy007

    Finishguy007 New Member

    Messages:
    4
    Location:
    Pgh Pa
    I guess I'm confused on what you mean by horizontal and vertical. Thx for taking this time to help.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Your total length of the horizontal run must be less than 1/3'rd the total length of the pipe's vertical run, or you need to bump the pipe size up one. The idea is that any horizontal pipe run still needs some slope to it, and you need to still have an air path for it to work as a vent in case for some reason it got some moisture in there (say rain, condensation, or whatever).
  7. Finishguy007

    Finishguy007 New Member

    Messages:
    4
    Location:
    Pgh Pa
    I think I'm picking up what your putting down. I understand the horizontal. But when you speak of vertical are you referring to the vertical rise of that horizontal pipe. This horizontal vent is say 30'. Is the vertical the distance this pipe goes from its beginning to where it ties into main stack? Sounds like just running 2"-3" up there is a safe call.
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