Vent size for full bath + washer

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by MrUgly, Nov 15, 2004.

  1. MrUgly

    MrUgly New Member

    Nov 15, 2004
    Hello all,

    I have been a lurker here for several months gaining valuable knowledge for my bathroom addition. Before I okay the plans with the inspector I thought I would ask what should proper size for the vents be. I plan to run a new vent out the roof just for this addition rather than tying into the existing vent.

    Here is what I have:

    1 1/2" vent coming off the vanity (1 1/2" drain, single bowl)
    1 1/2" vent coming off the shower (2" drain)
    2" vent coming off toilet (3" drain, vent is about 20" away from closet flange)
    I also need to tie a washer into the vent from the toilet.

    The sink and shower vents will join together above wall then run about 4' horizontally to connect into the toilet vent. The washer will connect on the vertical toilet stack about 10" off the floor. After the sink/shower vent ties into the toilet/washer vent it runs up about 8 feet to the roof.

    Do I need to bump the size of the toilet vent up to 3" after they all connect to accomodate all the vents or will 2" be enough ventilation. I am fine running 3" vent from the toilet to the roof if I need to. I live in Minnesota if that matters.

    There will be no other lines into this vent. Only the sink, shower, toilet and the washer.

    I would be glad to clarify anything I have been unclear about.
  2. cea

    cea New Member

    Nov 14, 2004
    The minimum vent size is based on the number of drainage fixture units served by the vent. For a secondary vent serving just the fixtures you listed, 2" should be sufficient. However, your code probably requires you to increase the vent terminal (from 12" or so below the roof line, on up to the vent outlet) to 3" or 4" to reduce the possibility of ice blockage (especially up there in the great white north). So it might be easier just to run the 3" all the way up. Check with your local inspector to verify vent and vent terminal sizing. Good luck.
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  4. MrUgly

    MrUgly New Member

    Nov 15, 2004
    RE: cea

    Thank you for the response. Your suggestion makes sense. I would rather run 2" until about a foot before the roof (as you suggested). I will go with this idea and see what the inspector says.

    Thanks again
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