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Old 03-09-2008, 12:07 PM   #1
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Air Gap for Dishwasher


Perhaps the licensed plumbers familiar with Arizona code can give me an answer on this.

Out here, sink-mounted air gaps are not found in newer homes, mostly only in older ones. Where there is a garbage disposal in place, the dishwasher drain hose normally connects directly to the garbage disposal's port without any air gap in-between. Occasionally, I run into a situation where there is a working garbage disposal in place AND also an air gap in-between.

The problem is that many of the new dishwashers discharge at a very fast rate and higher pressure and occasionally leak or belch water and food stuff right out the air gap and onto the sink. Changing the air gap and the hose does not help and the dishwasher is the dishwasher. The disposal's port is free and clear and the disposal is working properly. Similarly, the drains and P-trap are free and clear.

I understand why air gaps were used and required at one time but are they still required by modern day code IF the dishwasher connects directly into the garbage disposal? Seems that there is an inconsistency in what I find going from house to house within the same development or neighborhood and I'm curious to know if they are now just vestigal in most cases and unnecessary.

I appreciate any official explanation that one might be able to offer.

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Old 03-09-2008, 01:00 PM   #2
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Air Gap for Dishwasher


I'm not a plumber, but I believe there is an 'in' and 'out' on an airgap and I would check to see if it is connected in the correct order

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Old 03-09-2008, 02:32 PM   #3
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Air Gap for Dishwasher


AZ is under UPC Code, here we are to, we don't use the air-gap that sits on the sink top, we just hang the hose high up under the KS and connect to the disposal.
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Old 03-09-2008, 02:50 PM   #4
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Air Gap for Dishwasher


Many of the areas that required air-gaps have now found that they are pretty useless and just another expense and have done away with them being code. As long as the DW hose is run up to the top of the cabinet to form a loop (basically an upside down trap) it will not siphon from the DW. I agree that the newer DW's have lots of discharge pressure and the air-gap merely provided a place to cause a clog.
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Old 03-09-2008, 06:04 PM   #5
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Air Gap for Dishwasher


Based upon the replies, I got to Googling for the AZ code and came across a plethora of verbiage.

According to what I found, the Arziona code states as follows for residential, not commercial:

R4-48-108. Chapter 8, Indirect and Special Wastes
The Uniform Plumbing Code incorporated in R4-48-102(A) is modified as follows:
1. Sec. 807.4 is modified to read: The discharge pipe of a domestic dishwashing machine may be directly connected to the tailpiece of a sink drain, or into the waste "boss" of a food waste disposer without installation of an airgap fitting. The dishwasher discharge line shall be securely fastened as high as possible, but not lower than two inches (50.8 mm) below the flood rim of the sink.

Please correct me if I'm interpreting this wrong but I take that modification (revision) to mean that:

if the dishwasher's discharge hose is, let's say, attached to the back of the cabinet underneath the sink and it is placed high enough so that it is within two inches of the sink's rim and so that the bend in the hose forms a suitable "bell" shape then

it is within code to by-pass a troublesome air gap setup, eliminate it altogether and connect the discharge hose directly to the garbage disposal or the tailpiece.

Last edited by End Grain; 03-09-2008 at 06:07 PM.
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Old 03-09-2008, 06:09 PM   #6
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Yes that is what it says.
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Old 03-09-2008, 09:25 PM   #7
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Air Gap for Dishwasher


Thanks to all for the help and also to Ron for the interpretation!

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