best way to extend washer drain over a few feet

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by nj greenhouse, Aug 13, 2014.

  1. nj greenhouse

    nj greenhouse New Member

    Messages:
    6
    I am moving my washing machine over about 39 inches, which means it will be about 40 inches or so from the current location of the 1 1/2 inch drain pipe.
    In the pictures below you can see its current location next to the drain pipe and supply lines. I want to stack the washer and dryer and have them on the other side of the window in the picture. The 1 1/2 inch drain pipe has a proper trap, but no vent. I guess it needed no vent because it is right next to the main stack and therefore is "wet vented".
    My question is whether I can use the existing trap, cut right above it, and run a horizontal pipe (with a slope) over about 40" to a new drain pipe location for the washer (on the other side of the window in the picture? do I need to add a vent? What is the best way to drain the washer after I move it over to the other side of the window in the picture?

    Thanks for any suggestions
    Dan

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    Last edited: Aug 13, 2014
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    "Being next to the main stack" does NOT always mean it does not need a vent. In fact, unless it is a single story building without a basement, it may ALWAYS require a vent. If your trap is going in to that "Y", then it is NOT a proper connection and DOES need a vent. Unless you MOVE the trap to the new location, (do not try to add a second one there), you will create potential problems later.
  3. nj greenhouse

    nj greenhouse New Member

    Messages:
    6
    hj - the trap from the washer drain is currently below the y, that first thing above where the copper meets the iron hub.
    so, you are suggesting to cut into the 1 1/2 inch copper line right next stack, couple to pvc, extend it over about 40 inches, new p trap, then up a few feet vertical? where would vent go, what about cheat vent? do you have any pictures or diagrams to show me an acceptable way to extend a washer drain?

    Thanks
    Dan
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,139
    Location:
    New England
    First, since you're modifying what you have, you must bring it up to current codes, and that requires it to be done with 2" pipe, not 1.5". The stack, while it may have sufficed under the building codes way back (the house I grew up in built in the 50's was like this), doesn't mean with today's fixtures it would still always work properly. Today, we tend to have multiple bathrooms, and the flow in the main drain line just may not allow wet venting (and today, it is never allowed between floors). So, technically, you should also install a proper vent as well to move things. Also note that, especially if you're using a front loader, and you put it on a pedestal, the height of the stand pipe may be problematic and have to be adjusted somewhat.

    Today's front loading WMs can end up pumping a lot faster than the older, top-loading ones, and a 1.5" line often doesn't cut it. The codes change for a reason...remodeling requires you to catch up!
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    Oh, now I see it. Your ruler was obscuring the drain. In that case, since I assume that Y is draining something from upstairs, it MUST have its own vent. In that location, the trap will be subjected to both positive and negative pressures, and a "cheater vent" CANNOT handle positive pressures.
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