Dishwasher drain "high loop" vs. Air Gap questions

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by JerryR, Feb 10, 2014.

  1. JerryR

    JerryR Member

    Messages:
    246
    Location:
    Florida
    We had a dishwasher installed with a "high loop" rather than installing an air gap. I know I've read here that either works. I believe code in some places requires an air gap but previous DW did not have an air gap.

    The dishwasher drains into the disposal. At times my wife has complained of foul odor in the dishwasher . The only way I can see sewer odor entering the dishwasher is if the disposal p-trap is dry so I've instructed her to run a little water into the disposal sink side after using the disposal.

    A couple of questions

    1- can disposal p-trap get pumped dry with the disposal running?
    2- would there be a benefit to install an gap as I think this may be current code here. that would require boring a hole in the granite top which I prefer not to do if not required.

    JR
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,055
    Location:
    New England
    The reason for an air gap is overall safety...it is safer than just a high loop. Water and waste will take the path of least resistance, but throw in a disposer which can act like a pump, and stuff could go places it wouldn't normally go.

    If your water isn't hot enough, or your DW does not have a pre-heat setting (or it's turned off), it can leave residue in the cabinet. If there's a bit of plastic or something caught in the drain, it may not drain fully, or could trap some crud there that can't get past it. DW often like water at least 130-degrees, which is often hotter than your supply.
  3. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,248
    Location:
    Land of Cheese
    A couple possibilities- one is that she leaves the door shut all the time so the dishwasher does not dry out. This will cause a smell.

    The other possibility is that that the drains under your sink are done not quite right, so if you were to post a picture, we might be able to point out a problem if that is the case.
  4. wondering

    wondering Member

    Messages:
    106
    Also, some brands tend to have a problem with smells inside more than others.
  5. JerryR

    JerryR Member

    Messages:
    246
    Location:
    Florida
    We found that out the hard way. After recently redoing the kitchen we had all new Samsung appliances installed in the Kitchen. The Samsung dishwasher almost always had odor plus it would leave dishes wet no matter what cycle was used. This is due to condensation drying. It seems that Samsung and LG are notorious for not drying.

    Fortunately we bought the appliances from Home Depot. They took back the 3 month old Samsung dishwasher and delivered and installed a new Maytag. It is 10x better than the Samsung.

    Only once has my wife complained about smell with the Maytag. I think it may have been where the p-trap on the disposal side was pumped dry. Just a guess.

    JR
  6. edwardh1

    edwardh1 Member

    Messages:
    99
    Location:
    South Carolina
    bosch uses condensation drying (on my first bosch dw,) works well, does not bake the dishes with a heating rod, some condensation remains but not much. they are smaller inside, maybe needs to use the dw cleaner lemon material once a year.
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