Laundry stack - can pipe size be reduced?

Discussion in 'Plumbing Code Questions' started by mikeygstl, Nov 18, 2012.

  1. mikeygstl

    mikeygstl New Member

    Messages:
    6
    Location:
    Saint Louis, MO
    I am finishing off our basement laundry, and currently there is a 3" stack coming up out of the floor. The trap is under the concrete. Is it acceptable to reduce the pipe size to 2" in order to hook up to a washing machine outlet box, or is there a outlet box with a 3" spigot or hub connection? I fall under IRC here - they still go by the 2006 edition.
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,260
    Location:
    Land of Cheese
    The standpipe with trap can be 2", and needs to be above the floor. This can connect to the 3" line going into the floor. The trap below the floor will need to be removed.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,302
    Location:
    Bothell, Washington
    Between the 3" stack and the p-trap, you will need a vent.
    Trap above the floor.
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,260
    Location:
    Land of Cheese
    I do recall another member posting here that the 3" standpipe with the trap in the floor is specifically permitted by a local Missouri code. I didn't believe it at the time but did find it in the MO code.
  5. mikeygstl

    mikeygstl New Member

    Messages:
    6
    Location:
    Saint Louis, MO
    I do know the 3" stand pipe is permitted, with a trap beneath the floor, as it was inspected and passed justa few months ago. The problem I am having is that I now need to find a way to connect this stand pipe to a 2" washing machine outlet box.

    I'll talk with the inspector this afternoon when I pull the permit and report back what I find.
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