Washer Standpipe and Laundry Sink Drainage Reconfiguration

Discussion in 'Canadian Plumbing Code Questions' started by bpontin, Jan 14, 2017.

  1. bpontin

    bpontin New Member

    Jan 14, 2017
    We just moved into an older home and I want to move the laundry to a different location in the basement. I have been doing quite a bit of reading and found some excellent resources on both this forum as well as others and I think I have it figured out but I was hoping I could get a second opinion before I pull the trigger. The complication I am having is that most of the pictures/diagrams that I have seen with a standpipe and laundry sink have the laundry sink downstream from the washer standpipe whereas I want to do the opposite; laundry sink at the end of the line, washer standpipe downstream from the laundry sink.

    I have taken a picture of where I plan to move everything just for some context. You can see the 3" vertical line I will tie into on the left and the 1-1/2" vent on the right I plan to vent to.

    I have also attached a sketch of what I am thinking I will do. A couple of questions regarding the sketch:

    1. Does what I have proposed to do here look OK and to code? Is there anything that I am overlooking?
    2. Does the second vent line (the one on the right servicing the laundry sink trap) need to be there? Or can the vent downstream of the laundry standpipe act as a vent for both? I am guessing no since there is a chance that the standpipe will act as the sink vent and that's not allowed. The sink will be immediately next to the washer so there won't be more than 30" from the laundry sink to the vent.

    Any other comments would be appreciated.

    LAUNDRY 1.jpg


    Thanks very much!
  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    Do not tie the sink into the standpipe.

    Venting for the sink comes off the vertical and is at the high point of the santee. What you have now is an S trap that will siphon.
  3. Sponsor

    Sponsor Paid Advertisement

  4. bpontin

    bpontin New Member

    Jan 14, 2017
    Thanks for the response Terry. I have revised my sketch to put the trap for the standpipe above the horizontal drain. I think this should eliminate the issue of creating an S trap? My only concern here is that I am not certain that I will be able to keep the trap for the standpipe below 18". Is that a code requirement or a preference (6" - 18" above the floor for the standpipe trap)?

    Also, my second question still applies here, is the vent on the right that is servicing the laundry sink trap required? Or will the vent to the left of the standpipe wye work as a vent for both fixtures?


    Thanks again!
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Jan 5, 2008
    Test, Don't Guess!
    Land of Cheese
    Run the fixture trap arms horizontally to their respective stacks using sanitary tees. The stacks must tie into the horizontal drain using wye and 45's or combo fittings.
Similar Threads: Washer Standpipe
Forum Title Date
Canadian Plumbing Code Questions Dishwasher and Standpipe in Quebec Jun 18, 2019
Canadian Plumbing Code Questions Plumbing washer and sink and standpipe Jul 21, 2017
Canadian Plumbing Code Questions Code for a washer in Canada. Help me win (or lose) a bet. Jan 6, 2020
Canadian Plumbing Code Questions Moving Washer - remodel Nov 13, 2017
Canadian Plumbing Code Questions AAV Valve for washer? Jul 1, 2017

Share This Page