Washing Machine Stand Pipe/Drop In Sink DWV stack question.

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by WORKS/WORKS II, Jan 9, 2012.

  1. WORKS/WORKS II

    WORKS/WORKS II Retired Contractor

    Messages:
    3
    Location:
    Cleveland
    I resently retired from the Air Force and have lurked here over the years for much needed advise on the many places we have live requiring plimbing repairs etc . . . so thanks to everyone for the help. I am installing a Washing Machine Standpipe and drop in 8 inch deep cabinet sink off the stack in the attached photo. This 3 in stack services a bathroom directly above it (Toilet/Lav/Shower) As you can see this stack was offset using a 45 and a street 45 . What I would like to do is raise the offset higher up the wall, keep the abs clean out at the bottom and double stack two sani-tees, one for the washer stand pipe and one for the drop in sink.

    The yellow line (forgive crude drawing) is the proposed change to the stack offset location.
    The horizontal red lines are the new drains.
    The blue is venting that would go into attic and tie back into the 3 inch stack above the insulation.

    Drains and venting would be 2 in pvc and the proposed stack change (raising the offset) would be 3 in PVC with Fernco Shielded Proflex Connector.


    Second question, as an alternative, could I remove the clean out at the stack base and 45's and replace with a 3 x 3 x 3 y with a 45 taking the y vertical in 3 in PVC, double stack 3 x 3 x 2 sani-tees (one would come out of the wall for the sink) add a clean out above that and then reduce the new 3 in to 2 in and vent it and the stand pipe as shown in the second picture ?? Sorry to be such a pain and again . . .thank you for your assistance in advance.


    100_9010.jpg

    draw.jpg
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,837
    Location:
    Cave Creek, Arizona
    You are making the job too complicated. Just connect the sink to the washer arm with a combo then use its vent for the washer trap.
  3. WORKS/WORKS II

    WORKS/WORKS II Retired Contractor

    Messages:
    3
    Location:
    Cleveland
    Im stupid !!!

    I think I understand what your telling me, take a sani-tee off the stack run that out to the washer stand pipe, put a combo somewhere along that run going up and turn a sani-tee out for the sink drain continuing up as if that is the vent for both the sink and washer stand pipe ?? . . . . . the question that is still and issue for me - can I move the offset up so the sani-tee on the stack is low enough for the drain for the sink . . . . Im not familiar with what the stub out height would be for the sink trap ?? Thank you for your reply . . . .
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,134
    Location:
    Bothell, Washington
    You will need to move the offset up higher to make room for the fittings if you are adding a washer and a sink.

    I would talk to your plumbing inspector first before doing it hj's way.
    Some places don't allow wet venting a laundry sink over a washer. They don't in Washington State. That's why I try to answer these questions so that it applies anywhere. I don't assume you are plumbing in Arizona.

    I would have the sink on hand first, and then you will know how high you can run the plumbing.
    Last edited: Jan 9, 2012
  5. WORKS/WORKS II

    WORKS/WORKS II Retired Contractor

    Messages:
    3
    Location:
    Cleveland
    Thanks Terry . . ..both for the answer/comments/suggestion but for all you guys do on this site . . . . . its a EXTREMELY VALUABLE resource !!! I am thinking about double stacking two sani-tees . . . . run the washing machine on the bottom one and the sink on the second one venting both 6 inches or more above the washer standpipe and then take the vent up into the attic . . . similar to this picture that has been posted on here before with the vent going up for the attic tie in - not back into the stack like its a vent . . . . what would you think of this ??

    maybe.jpg
  6. Hammerlane

    Hammerlane Member

    Messages:
    252
    Location:
    Ohio
    I believe what you posted above is one of my doctored up photos. But your description does not match the photo.

    The photo above shows the washer flowing past the sink drain which is NOT the ideal configuration. Your description above talks about double stacking the San-Ts and running the washing machine on the bottom branch drain and the sink on the upper branch drain. See photo below:

    Attached Files:

  7. Hammerlane

    Hammerlane Member

    Messages:
    252
    Location:
    Ohio
    Here's another setup:

    Attached Files:

  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,837
    Location:
    Cave Creek, Arizona
    We can wet vent a sink over a washing machine, but not the other way around. I am not sure why any area would not allow it, because there are no "hydraulic" problems with that method.
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