Draining sink into vent pipe

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by MJCMendonca, Apr 19, 2014.

  1. MJCMendonca

    MJCMendonca New Member

    Messages:
    4
    Location:
    ON
    Have been reading this site for quite a while and it was absolutely brilliant when installing my Toto Aquia 2 toilet a while back.

    This is my first post though...

    I am working on a bathroom renovation upstairs and I am now working on converting my previous single sink plumbing to a new double sink setup. I opened the wall to see what I am looking at, and took a picture so that you could see it too. (please see picture below).
    SinkDrain.jpg

    My question is ... can I cut into the pipe on the left, which I believe is a vent (this is on the second floor and the attic is directly above this level) and run the drain for the left sink there? and leave the right pipe alone and plumb the right sink there?
    Piping is all 1 1/2.

    If that is not possible/recommended, would you please provide other options?

    Again, thank you very much for your help.

    Mo Mendonca
    ON, Canada
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,811
    Location:
    Cave Creek, Arizona
    No, it is the vent for the downstairs bath so it cannot be used as a drain. Offset it to the left and then connect the new sink to the existing drain line, but do it properly.
  3. MJCMendonca

    MJCMendonca New Member

    Messages:
    4
    Location:
    ON
    Thank you very much! I will offset the vent to the left and will cut out the santee on the right. From there the easier option would be to install a double santee and run from there. Would that work okay?
    Also, not sure if it matters, but underneath this room I have the laundry. The main floor bath is fairly away from this location.


    Thank you so much!
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,811
    Location:
    Cave Creek, Arizona
    I would NOT install a sanitary "cross" nor would our inspectors approve it. The proper fitting is a "back to back" fixture fitting. It is NOT a sanitary cross, nor is it a "double combo" but rather a fitting between those two. It eliminates the functional problems caused by using either of those two fittings.
  5. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    Depending on what the vent on the left hand side is venting, then you could possibly cut into it and tee off for your second sink making it a wet vent. Bare in mind that a 1.5" went vent can only receive 2 fixture units (this doesn't include the most downstream fixture). If the vent is only venting one fixture (not including a toilet) then you could cut into it and make it a wet vent. This is permitted in Ontario.
  6. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    We cannot wet vent between floors in the U.S.
  7. Sean Beck

    Sean Beck Plumber

    Messages:
    68
    Location:
    Toronto, Ontario, Canada
    You can in Ontario, providing there is no more than 4 Fixture Units per floor drained to the wet vent.
  8. MJCMendonca

    MJCMendonca New Member

    Messages:
    4
    Location:
    ON
    Thank you very much for all the detailed information! You guys rock!
    I believe the the left side pipe is venting the laundry sink - which is directly underneath this bathroom. But you just never know...

    I did however, follow hj recommendation and moved the left side pipe out of the way (I added elbows and moved the line to the left) and used a back-to-back fitting (the guy in the store here called it long double tee) on the right pipe.

    Again, thank you so very much!
  9. MJCMendonca

    MJCMendonca New Member

    Messages:
    4
    Location:
    ON
    This is what it looks like now...
    SinkDrain2.jpg

    Looks okay?

    Thanks!
  10. JerryR

    JerryR Member

    Messages:
    250
    Location:
    Florida
    Last edited: Apr 19, 2014
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