Venting

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Mikect05, Nov 12, 2011.

  1. Mikect05

    Mikect05 New Member

    Messages:
    11
    Location:
    CT
    Hi, I am completely remodeling our first floor bathroom. I have a question about venting it. Our main drain pipe leaving the house is 3". I would like to have the main vent stack to be 2" so that it can fit in the wall. It will serve a Toilet and a Bathtub, Once it gets to the attic I will transition it to 3" and tie in a 1 1/2 vent from the lav, and a 1 1/2 vent from the shower in the same bathroom. I will also tie in a 2" vent from the basement that serves a toilet, lav, and shower. Will this suffice as my main vent exiting the roof at 3" the same as the main drain pipe, Or does it need to be 3" from drain pipe?
    Thank you very much.
  2. Mikect05

    Mikect05 New Member

    Messages:
    11
    Location:
    CT
    No comments huh? I am now running the 3" vent directely from the main drain line up through the roof. Is there any problem with putting a few bends in it as long as it stays at least at a 45 degree angle up?
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,130
    Location:
    Bothell, Washington
    2 x 2.0"
    1 x 1.5"
    =
    3.0"

    Two two inch pipes and one 1-1/2" pipe is the same area as a 3" pipe.
    Four 2" pipes equals one 4" pipe area.
  4. Mikect05

    Mikect05 New Member

    Messages:
    11
    Location:
    CT
    Sorry I need some clarification on this as I have had two plumbers tell me conflicting information. At first I was made to believe that as long as all fixtures were vented properly than I could join them together above flood height or 42" as a 3" as that is my drain size and have that exit roof.
    Then I was told that that is not adequate and I needed to have a vent from the main drain line at the same diameter run unreduced all the way up through the roof.
    As I did not get a response I did run a 3" vent off of the toilet arm and have it coming up through my bathroom floor under the tub surround from there I was going to box it in along the wall and up into the attic and out the roof.
    What if I was to branch this 3" into 2 2s and a 1.5 in the dead space around my tub surround and angle these up between studs and into attic where I can once again bring them together as a 3" and then join in the other vents from fixtures before exiting the roof?
    Thank you so much for your help, it is very much appreciated!!
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,231
    Location:
    Maine
    Your code requires one vent that is 1/2 the size of your main to exit through the roof so in theory a single 1 1/2 vent takes care of things.
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