Dishwasher Drain Problem

Discussion in 'Plumbing Forum' started by Skeezix, Aug 21, 2019.

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  1. Aug 21, 2019 #1

    Skeezix

    Skeezix

    Skeezix

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    The drain for my dishwasher is connected in an unusual way. The following shows what you see when you open the doors below the dual sink:
    01 20190819 Kitchen Drain 640 px.jpg

    Here is what's behind the garbage disposal. The dishwasher is behind the wood at the left of the drawing and its drain is shown at the bottom:

    Kitchen Drains Drawing.jpg

    Behind the drywall the two drains (marked "to Sewer) lead to a Y and then to the clean-out. I think, that is.
    And I assume the dishwasher drain shown at the left of the image is configured as an "air gap". I don't know what's behind the drywall, but I do know there is only one 1.5-inch pipe running from somewhere below the Clean-Out to the main sewer (because I can see if it I remove the basement ceiling tiles). Here is my problem:

    The top of the air gap is just below the underside of the counter top. If the waste pipe from below the Clean-Out clogs up, waste water can and will rise up above the level of the Clean-Out and eventually come out of the two "Open" parts of the "air gap" depicted on the top left of the drawing. Twice now that has happened and the water seeped into the basement ceiling and stained it. I am thinking about installing an air gap that would empty into the sink rather into its own dedicated pipe. However, I don't know what to do with the dishwasher drain to the sewer other than installing a cap at the wall.

    Also, anyone know the purpose of the dishwasher connection to a separate waste pipe rather than to the sink? Other than esthetics, that is?

    Any suggestions for me?
     
  2. Aug 21, 2019 #2

    Snoonyb

    Snoonyb

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    The drawing on the left is so illegal words cannot describe it.

    Here are several examples of the "high loop" that is the proper method when you are not using an air gap;garbage disposal high loop
     
  3. Aug 21, 2019 #3

    Skeezix

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    That's odd. The dishwasher drain is like the following image that I found at this link:

    Dishwasher Drain with Standpipe.jpg

    I just don't like the open ends of the standpipe.
     
  4. Aug 22, 2019 #4

    nealtw

    nealtw

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    Have you looked at the roof to see if there is a vent above this area for the plumbing.
    I would knock the little plug out of the pipe in the side of the garberator at the top and run the dishwasher there like most everyone else
    [​IMG]
     
  5. Aug 22, 2019 #5

    Snoonyb

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    That's why it's illegal, it's an open waste line. You can cap it or install AV vent, preferably to the exterior.

    It would be easy to connect it like one of the examples I provided a link to.
     
  6. Aug 22, 2019 #6

    Skeezix

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    I plan to connect to the garbage disposal by running an extension up to the height of the counter top and then back down to the garbage disposal. Then I'll cut the existing standpipe configuration and plug the hole. Easy to do, a bit harder in reality though because the dishwasher drain plumbing is glued rather than threaded and space there is at a premium.

    Yes, there is a roof vent pipe directly above the kitchen sink.

    And yes, that's a real Rube Goldberg plumbing job there!

    03 20120530 DW Drain 800 px.jpg
     
  7. Aug 22, 2019 #7

    Snoonyb

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    you should be able to find an extension hose and attach it via a coupling.
     
  8. Aug 22, 2019 #8

    Fireguy5674

    Fireguy5674

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    Are you familiar with local codes? Where I am the city does not allow dishwashers to be drained into or through disposers. We are required to install an extension tube with a dishwasher barb and run the dishwasher drain into that with the high loop as shown in some of the drawings on Snoonyb's link. Not sure why but it is the way we have to do it.
     
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  9. Aug 24, 2019 #9

    Skeezix

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    I live in Colorado. I looked up dishwasher drain requirements in the Colorado statutes. It says all dishwasher drains must have an air gap. Isn't the image in Post #3 an air gap, albeit one that will overflow onto the floor should the drain pipe be clogged somewhere? I was thinking about installing an air gap like that one and running the tube from it into the garbage disposal, and closing off the second drain (shown in the drawing in Post #1). Do you think that will satisfy the statute? I don't recall anything in the statute that discusses the type of air duct.
     
  10. Aug 24, 2019 #10

    Snoonyb

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    "Generally" the method to overcome the rule is a high-loop.

    The high-loop exception is applied when a dishwasher is installed and the kitchen sink is not changed out.

    You can msg. your building dept, or, you can stop by and ask.
     
  11. Aug 25, 2019 #11

    Puddlesx5

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    All of the drain methods that I have seen on this post are an air break. The suction is broken by air. If the sewer backs up it could siphon back to the dishwasher. An air gap requires a 1 inch gap of air. Most home centers sell a kit with an air gap, stainless steel hose clamps and 7/8 hose to complete the job.
    Some states only require a high loop which just get the hose as high as you can under the sink.
    I would avoid running the drain through a garbage disposal (especially the cheaper ones). The drain holes have a tendency to plug or corrode shut.
     
  12. Aug 25, 2019 #12

    Puddlesx5

    Puddlesx5

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    This is an air gap and legal. It does look bad but is approved an an air gap.
     
  13. Aug 25, 2019 #13

    Skeezix

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    @Puddlesx5 - I appreciate your comments. I was wondering why connecting the dishwasher drain hose to the garbage disposal was not recommended, now I know.

    I'll call the City tomorrow and find out more. Probably will replace the pipe from the sink to the P-trap with one that has a fitting for the dishwasher.

    Thanks again!
     
  14. Aug 25, 2019 #14

    Snoonyb

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    The "air gap" became a requirement in the 1960's and is the design approved by the ICBO, to prevent waste water being introduced into the potable water system when primary water pressure is interrupted.

    In your case, when the 1-1/2" waste line plugs the overflow is into the cabinet. With the DW drain connected thru an air gap or high-loop, then to the disposal, and in over 45yrs. I've never seen a disposal DW discharge port clogging, any backup would be contained in the kitchen sink, which has the capacity to contain that discharge below the flood rim.

    A few of the new DW have a bit-in back flow preventers, some both supply and discharge.
     

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