How do I handle this dishwasher drain setup?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by TubeGuru, Aug 27, 2010.

  1. TubeGuru

    TubeGuru New Member

    Messages:
    11
    Location:
    Redmond, WA
    I took the old GE dishwasher out tonight and found that there's a 5/8" copper pipe going through the base of the wall and off under the house somewhere (I'll go into the crawl space tomorrow to investigate). The old dishwasher was connected via a 16" rubber hose. Should I connect the new Kenmore with the new hose running flat to the drain, or should I loop it up the back wall 20" as the instructions suggest? The new hose is much longer.

    Here's a pic of the situation.

    Thanks!
    Walt

    dwdrain.jpg
  2. Jerome2877

    Jerome2877 In the Trades

    Messages:
    397
    Location:
    BC
    Yes it should loop up then back down. This is to prevent waste from going back into the DW in the event that your drain backs up. Let us know what you find in your crawl space, it should have trap.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,362
    Location:
    Yakima WA
    There are 2 ways to connect a DW drain. Some local codes require an air gap which is on top of the counter. The drain hose come from the DW to the air gap then from the air gap to the sink drain. The other method is allowed by other local codes. This method is to loop the drain hose from the DW up under the counter top then down to the sink drain. In both methods, the connection to the sink drain is via a special tailpiece that has a connection stub for the hose and the connection is ahead of the sink's P trap. If you use the loop method, you must be sure the hose is attached at the high point in the loop so that it will not kink.
  4. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Couple of problems...we need to see what's down below. The drain needs connect through a trap, and through and air gap. We don't know if either of those things is happening. And the pipe seems just a little small. Not sure if it is adequate for the dw pumped drain.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,183
    Location:
    New England
    It all depends on where that line eventually goes. If it runs around to the sink, it could connect like a 'normal' install, where the DW is next to it. As long as there's a minimum of a high loop before it hits the trap (and an air gap is required and recommended even if it isn't), getting the discharge to that point may very well work with what you have. WHen the plumbers installed mine, they used similar hose to get it to the sink area (mine is around the corner of a U-shaped kitchen from the sink). The hose should not be smaller than the diameter of the existing outlet hose of the DW.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,879
    Location:
    Cave Creek, Arizona
    Impossible to answer your question without seeing the rest of the drain line. If it loops up at the final connection, then you do not want to loop it at the diswasher also. I assume the DW is not next to the sink.
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,152
    Location:
    Bothell, Washington
    In the Redmond and Seattle area, the drain you are looking at is connected to a "Johnson Tee", invented by a Seattle plumbing inspector and used widely in the State of Washington. The 1/2" copper goes up above the counter height and then drops into a Johnson Tee, which has an air gap through the outer siding. The drain then drops into a 1-1/2" standpipe and p-trap.
    This arrangement gives you an air gap above the counter height, and a drain that is trouble free for years.

    [​IMG]
    Last edited: Aug 28, 2010
  8. TubeGuru

    TubeGuru New Member

    Messages:
    11
    Location:
    Redmond, WA
    That's great news! Based on Terry and HJ's answers, I can use the existing drain, and should not add a loop at the DW. The DW already has a built-in loop in the back. And yes, the DW is next to the sink.

    I went under the crawl space earlier and was baffled not to find anything at all (except spiders).
  9. TubeGuru

    TubeGuru New Member

    Messages:
    11
    Location:
    Redmond, WA
    I scraped the paint off of the air gap vent and didn't find any holes. So I presume I should drill a 1/4" hole in the cap?

    johnsonvent.jpg
  10. Terry

    Terry Administrator Staff Member

    Messages:
    15,152
    Location:
    Bothell, Washington
    Yes, Jamie can drill the hole while he's out there.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,879
    Location:
    Cave Creek, Arizona
    Did the Johnson drain fitting ever get IAPMO, or other, approval? Originally, they did not want to invest the funds for certification since it was a substantial amount. It looks like that center piece is designed to be "snapped out" after the drain is installed.
  12. Terry

    Terry Administrator Staff Member

    Messages:
    15,152
    Location:
    Bothell, Washington
    It's a 3/4" PVC glue on cap. We just drill a hole through it.

    IAPMO?
    I don't know, more like one of those locally approved things that inspectors do. I've been installing these things since 1974, and it was being done long before that.
    Last edited: Aug 29, 2010
  13. shacko

    shacko Master Plumber-Gas Fitter

    Messages:
    561
    Location:
    Rosedale, Md
    >>>Dishwashers require an air gap. An air gap can be a deck mount or a Johnson tee type with required trim vent. (UPC 807.4 & 314.0 with exceptions per manufacturer)<<<
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