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Options for dishwasher drain in interior wall and no kitchen sink

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  • Options for dishwasher drain in interior wall and no kitchen sink

    Hi there,

    I have what seems like it may be a unique problem with regard to dishwasher placement and options for drainage. Here goes:

    I'm interested in having a dishwasher installed in my kitchen on an interior wall. This is across the kitchen from the sink which is on an outside wall. There is no option for installing the dishwasher near the sink or even on that same outside wall.

    At the location I'd like to install the dishwasher, there is a drain and water supply in the wall that is associated with the free-standing pedestal sink located on the other side of that wall in the bathroom. The drain in the wall is vented to the roof and I can access it and the bathroom sink's water supply by opening the wall behind where I'd like the dishwasher to go. The problem is in the draining/venting of the dishwasher. Obviously, I cant use an air vent device as there is no sink into which overflow water would flow.

    I know about the "loop method" of hanging the dishwasher drain hose up high before it goes into the drain pipe but am wary of a "sealed" drain system that lacks siphon breaks (I don't want sewage or bathroom sink drain water to get into the dishwasher). I also have seen reference to a "Johnson Tee" method of drainage but always in the context of being vented to the outside. That wouldn't be possible given that this is an interior wall installation.

    The closest analog to this problem might be the idea of a dishwasher installation in an island--not anywhere near a sink. How would draining something like that be handled?

    By the way, we go by the UPC in my area which I think basically states that you must use an air vent and put the drain into your sink drain -- don't know how one is supposed to do that if there isn't a sink to go into! Lastly, what about P-trap? This wouldn't be draining into a sink drain but into a drain pipe.

    Hope that this is relatively clear and thanks up-front for any advice!


    Eric in Olympia WA
    Last edited by email4eric; 01-06-2009, 01:34 AM. Reason: Added information

  • #2
    Re: Options for dishwasher drain in interior wall and no kitchen sink

    Maybe I'm the best candidate to reply for you since I'm the slowest typer here and this subject requires a "medical journal" sized explination.And I cannot afford to type till lunch time this morning.

    It is not like a guy can cut a hole in the wall and splice in a couple of tees.
    Good call on the trap.
    This is only one of the many other very important(understatement)variables involced in doing a project like this.Drain hose CANNOT be directly installed in to trap.You need an air Gap/break.
    If this is going to be done correctly and not end up looking like some hack together piece of junk you really need
    to have a competent plumber help you on this.
    I hope you are going to at least have a cabinet and top to secure the machine to.


    • #3
      Re: Options for dishwasher drain in interior wall and no kitchen sink

      My best advice is to rethink the dishwasher location. It is most convenient if next to the kitchen sink.

      The UPC requires an air gap...period. In my CA experience, inspectors are inflexible on this. You could install a standpipe, like a washing machine drain, next to the pedestal sink. Paint some daisies on it, or something.


      • #4
        Re: Options for dishwasher drain in interior wall and no kitchen sink

        Thanks for the replys!

        Yeah, I'm looking into getting a plumber or two to come out and see what possibilities exist. I cannot believe that you are only allowed to put dishwashers next to kitchen sinks -- that doesn't make sense to me (though much in the world doesn't).

        I have no options on placing the dishwasher in an alternative location. The location chosen has a suitable opening in the cabinet run on the interior wall. There is no space whatsoever for it on the cabinet run where the kitchen sink resides (outer wall where fridge followed by sink followed by stove followed by closet lives).

        Yes, the location where I'd like it to go is an area where the cabinet stops and the counter continues so it is a conventional install in that regard. It's just the drain issue on an interior wall that is stumping me.

        Anyone know how they do it in kitchen islands?

        Thanks again!



        • #5
          Re: Options for dishwasher drain in interior wall and no kitchen sink


          I had two local licensed and bonded plumbers come out and take a look at the situation. Both stated that connecting the dishwasher to the drain pipe in the wall without an air gap was "no problem" and is how they stated they always do it. Both acknowledged that it isn't code and both said that they've been doing it that way for xx number of years without problems, etc., etc.

          They both stated that they would install the drain with a loop up high to the underside of the counter like you commonly hear about. One stated that if there was a backup, it would come out of the bathroom sink before it ever came into the dishwasher as the dishwasher drain would be installed into the drain pipe at a place higher than the bathroom sink drain plugs-in. He also said that the dishwasher usually has a check valve to prevent back flow anyway.

          They both seemed to think that air vents were not necessary and one even rolled eyes when I brought-up the "being to code" issue.

          So much for getting professional opinions!



          • #6
            Re: Options for dishwasher drain in interior wall and no kitchen sink

            I realize it may be a little late, but have you had a professional kitchen/bath designer involved? Your layout of frig/sink/stove does not sound optimal.

            Your designer should carry a ticket like this: and even places like blue and orange usually do have certified designers who may help you for free!
            Last edited by lovetheUSA; 01-10-2009, 09:09 AM.