No high loop or air gap in my dishwasher/disposal setup - what to do?


Old 02-16-09, 04:09 PM
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Question No high loop or air gap in my dishwasher/disposal setup - what to do?


While repairing a garbage disposal problem, I noticed that the plumbing coming from the dishwasher did not include a high loop or an air gap. The line ran along the bottom of the cabinet then went straight up to the garbage disposal. I then realized that whenever I ran the dishwasher, on its draining cycle, water would start flowing up from the garbage disposal making a really nasty smell.

I have no hole to install an air gap. I suppose I could fiddle with the hose to create some sort of high loop setup. I guess what I am trying to resolve are two issues/problems:

1) Preventing the disposal-side of the sink from filling up with water when the dishwasher drains

2) Prevent backflow from the garbage disposal into the dishwasher (im not actually sure this happens, but I'd like to be safer than sorry.

So - what should I do? What is code in Oregon? My home was built in 1991 so I figured this wouldn't be a problem, but I guess I am wrong...

Thanks in advance!
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Old 02-16-09, 04:25 PM
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By the way - it's a Kenmore 665. I have been trying to find a manual that explicitly states how to install it and whether it has its own air gap or high loop thing built-in but so far no luck..
Old 02-17-09, 11:06 AM
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all you need to do is take the dishwasher hose and attach it somehow, without kinking or restricting it, as high up in the cabinet as possible (preferably the bottom of the counter top).

as for the backing up into the disposal side f the sink i would pull the drain pipes apart and see if there is anything restricting/clogging them. if not then your disposal may be clogged and/or need replaced
Old 02-17-09, 01:01 PM
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Some jurisdictions require a countertop type anti-siphon device:

Fig 1. Example of typical countertop anti-siphon device.

some will allow the installation of a "high loop" instead:

Fig 2. Example of typical under sink "high loop" installation.

Some dishwashers (according to the manufacturers installation instructions, anyway) don't require external anti-siphon protection, their instructions may or may not be accepted by the local authority having jurisdiction (AHJ).

So what it really comes down to is what's acceptable to your local building department.


I believe most Kenmore dishwashers were made by Whirlpool, most of the Whirlpool's I've seen specify a high loop in the installation instructions.


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Old 02-17-09, 03:54 PM
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The purpose of the "high loop" or mechanical "anti siphon device" is to prevent the waste water from the kitchen sink from entering the bottom of the dishwasher when draining the sink basins. The anti siphon device is a safer way of accomplishing this as it incorporates an air gap making it almost impossible for bacteria to reach the clean dishes, whereas a high loop would only be a problem if both sinks were full and drained at the same time, or the drain from the kitchen sink were plugged partially and the waste water can travel back into the bottom of the dishwasher basin. Once the dishwasher starts its cycle, that waste water combines with the fresh water and is splashed onto your dishes, hopefully getting pumped out and cleaned on the next cycle.

Typically, when the dishwasher is in its drain cycle, you will hear a gurgling noise coming from the kitchen sink drain. If any water or waste is backing up the line, there is some issue with the drain itself as Dan has previously mentioned.

Installing a high loop is quite simple whereas a anti siphon device will entail drilling into your counter top and installing the appropriate device.

Call your local inspectors office to find out which type of protection they require in your city/town.
Old 08-08-11, 10:06 PM
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Hello Michael, I have a question. I have a dishwasher drain connect to Disposer like the picture on the right side of Figure T. But why everytime we use dishwasher, the water gusts out from the airgap it never goes into disposer..I check the disposer and confirm connection is right and has hole into the disposer from where the tube connection is. Any advise how to fix this problem?
Old 08-08-11, 11:30 PM
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The right-hand picture of figure T does NOT have the air gap but uses the "high loop" method.

If your air gap is properly piped, the dishwasher hose connected to the side, or "Y" port of the air gap with the bottom port of the air gap connected to the dishwasher then there is something obstructing the air gap itself, the hose to the disposal or the "knock-out" plug in the disposal connection is still in place.

Has the garbage disposal been replaced? Did the dishwasher EVER drain properly?
Old 08-09-11, 03:28 AM
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It is funny how you mention this problem now, as I just had a code class on Saturday and this exact problem was discussed. In NH we do not use Air Gap method but the High Loop instead. We were discussing how food particles from your dishwasher can flow into the Air Gap device and cause it to become stuck in the open position causing the messy problem you are left with. Take the air gap apart and flush it out with clean water, or replace it.
Old 08-09-11, 05:43 AM
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Knock-out plug nor removed when dishwasher was installed?


If the disposer has never worked properly, it's also possible the knock-out plug has left in place when it was installed:


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