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Dishwasher Req'd to Drain to Disposal?

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  • Dishwasher Req'd to Drain to Disposal?

    Hi, while doing a minor kitchen remodel with new sinks and faucets, I discovered the our ten-year-old house was originally plumbed with the waste line from the dishwasher draining directly to the sink waste line rather than going through a garbage disposal that sits right next to the dishwasher. (The disposal's dishwasher inlet knockout plugs are are still intact, so it's been this way since the house was built.)

    Is this Okay? It's been fine for ten years and I know that if there is no disposal, then this is acceptable, but I'm seeing some reports that a connection to a disposal, if one exists, is required by code and highly recommended.

    Thanks

  • #2
    Originally posted by whizmo:
    Hi, while doing a minor kitchen remodel with new sinks and faucets, I discovered the our ten-year-old house was originally plumbed with the waste line from the dishwasher draining directly to the sink waste line rather than going through a garbage disposal that sits right next to the dishwasher. (The disposal's dishwasher inlet knockout plugs are are still intact, so it's been this way since the house was built.)

    Is this Okay? It's been fine for ten years and I know that if there is no disposal, then this is acceptable, but I'm seeing some reports that a connection to a disposal, if one exists, is required by code and highly recommended.

    Thanks
    You did not state what area you are in so it may vary somewhat.

    The drain to the dishwasher is considered an indirect waste line. You are not required to drain the line to a garbage disposal. Draining the dishwasher to a branch tail piece is considered legal. I would recommend draining to the disposal unless you do a good job of prewashing your dishes.

    If you live in an area using the Uniform Plumbing Code the dishwasher drain hose must be drained through an air gap prior to its connection to the plumbing drain.

    If you live in an area using the International Plumbing Code you can eliminate the air gap but then must attach the hose to the bottom of the drain board prior to connecting it to a plumbing drain.

    Mark
    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

    I never lost a cent on the jobs I didn't get!

    Comment


    • #3
      Mark, thanks for prompt reply.

      I live in the Seattle area, WA state.

      To give further info, the dishwasher is adjacent to two kitchen sinks, a smaller one with a disposal next to the dishwasher and the main sink without a disposal. When the plumbing was roughed in, it appears they put in two identical waste lines under each sink; I assume are in common behind the wall. As currently plumbed, one waste line drains the main non-disposal sink and the disposal from the other sink, the other just drains the dishwasher, via a trap and an air gap.

      I'm guessing that this setup is acceptable, but that it would be better to drain the dishwasher
      through the disposal. If I do this, then I could either plug the extra waste line, or plumb the disposal to this waste line rather than having it connect to the other sink.

      Thanks again for the help.

      Comment


      • #4
        I will offer the folloeing advice:

        1) Your dishwater drain should go through an airgap (mounted on the deck of your counter top, or elsewhere). I don't know what code Washington goes by, but in my opinion the UPC has far better requirements than the IPC.

        2) It should be connected to you disposal inlet. This is not code, but the best method.

        3) What ever code you are working under, does not mean you cannot exceed it. Codes are minimum standards. For your home, why not go the distance. It is the health of your family that really matters in any plumbing installation. Please take the health considerations seriously, regardless of the minimum standards.

        the dog
        the dog

        Comment


        • #5
          Thanks,

          I've confirmed with a plumber locally that while a connection through the disposal is preferred, there is nothing about plumbing it to a waste line (with an air gap and trap) that is a problem or that doesn't meet code - this is how dishwashers are plumbed that have no disposal. It is mainly just an issue of putting additional solid waste loads on the plumbing with increased risk of clogging - we'll just be sure to scrape the dishes well.

          - Mark

          Comment


          • #6
            Originally posted by whizmo:
            Thanks,

            I've confirmed with a plumber locally that while a connection through the disposal is preferred, there is nothing about plumbing it to a waste line (with an air gap and trap) that is a problem or that doesn't meet code - this is how dishwashers are plumbed that have no disposal. It is mainly just an issue of putting additional solid waste loads on the plumbing with increased risk of clogging - we'll just be sure to scrape the dishes well.

            - Mark
            It's your house, pipe it the way you want. The correct way would be to pipe it into the disposal.

            Do it your own way. It will create work for plumbers.

            the dog
            the dog

            Comment

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