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Thread: New Dishwasher having air gap overflow

  1. #1
    DIY Junior Member chitowngreeny's Avatar
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    Default New Dishwasher having air gap overflow

    I recently just had a 15 year old dishwasher replaced with a new GE dishwasher. I never had any air gap overflow issues with the old dishwasher. The previous installation was connected to an air gap, so the installer connected the new dishwasher in the same manner. I live in Chicago so i "think" an air gap is still required per code (or a high loop i'm sure). Regardless, during certain drain cycles on the dishwasher, the air gap will overflow water (about a cup or two) out the top of the air gap cap (without the decorative air gap cover on) and into the sink and counter. I say "certain" drain cycles because it doesn't happen every time...when it's a full drain cycle, the dishwasher pumps out thru the air gap just fine (pumps for like 15 seconds), but when it's a short duration drain cycle (where the dishwasher only pumps out for 3-4 seconds) then it overflows.

    Other facts...
    - the drain line from the dishwasher to the air gap was replaced new.
    - there is nothing clogged in this new drain line and I connected some plastic tubing to the top of the air gap (without the cap on) and let it drain from the air gap into the sink to see if any debris was in there.
    - I do have a garbage disposal, but drain line #2 (coming from the air gap) does not connect to the disposal inlet underneath the sink...it has it's own dedicated connection into the wall with a P trap.

    is it possible that during a "short duration" pump out of the dishwasher, the water draining from the air gap into the drain line #2 doesn't have enough head pressure to "push along" the water already in the P trap, and thus backs up?

    Also, should I just connect the air gap drain #2 line to the disposal inlet as most air gaps are connected? If I do that, how do I cap the previously used drain pipe once I remove the rubber hosing? I don't want to leave it open and create a drain vent underneath my sink!

    any help would be great...thanks so much!

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    I have bad luck with air gaps bought at a hardware store.
    I use the Dearborn airgaps from the plumbing supply.

    It's not the pressure from the dishwasher, it's draining by gravity downward once it hits the air gap.

    Last edited by Terry; 11-19-2012 at 09:10 AM.

  3. #3
    Test, Don't Guess! cacher_chick's Avatar
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    If you have not already, I would start by cleaning the drain downstream of the air gap. If the drain is restricted, the air gap will be the point of overflow.

  4. #4
    DIY Junior Member chitowngreeny's Avatar
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    UPDATE: still having the problem...I've cleaned the drain downstream of the air gap and used Draino on the kitchen sink just in case it was a clog somewhere in combined drain pipe...but to no avail.

    As I mentioned in my original post, the overflow only happens during a very specific cycle of the new dishwasher. After a normal drain cycle, there is still water in the line from the dishwasher to the air gap...that water sits there in the line during the next wash cycle...then there is a very short pump cycle (about 5 seconds)...it's this cycle when the air gap overflows...it's as if the flow during this 5 seconds is too much to "fit" in the outer ring spacing that is the drain downstream of the air gap...is this possible? Are there air gaps that have a taller core that would fix this? Or any ideas on what could still be causing this issue?

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
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    I mentioned before that some air gaps don't drain as well. I use the Dearborn brand.

    Last edited by Terry; 11-19-2012 at 09:11 AM.

  6. #6
    DIY Junior Member chitowngreeny's Avatar
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    thanks Terry...I will order a Dearborn air gap and go from there!

  7. #7
    TROJAN WORLDWIDE SALES RP MACPLUMB 777's Avatar
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    Also you need to check the drain hose from air gap to drain see if it is kinked or has some restriction in it, that is what is causing your problem

    maybe when the installer was working he twisted the hose a little bit or
    something like that

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  8. #8
    DIY Junior Member chitowngreeny's Avatar
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    UPDATE: I replaced the existing air gap with a Dearborn Air Gap I purchased...installed it...and everything works great now! Thanks so much Terry, and everyone else, for your help and suggestions! Next...leaky bathroom sink faucet...see new post shortly...

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