Dishwasher drain line - air gap how-to

cramponApril 29, 2012

Hi all,

A quick question as I prepare to drill a hole in my sink cabinet to run the diswasher drain line. I've seen a few tutorials online that show the drain line coming in at the bottom of the sink cabinet, then strapped at the top of the cabinet to create an air gap.

Couldn't I get the same effect without the strapping step by putting the hole for the drain hose at the top of the sink cabinet? Is there a reason why I shouldn't do that?

Thanks!

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brickeyee

"then strapped at the top of the cabinet to create an air gap. "

That is not an air gap (required in some locations) but a 'high loop' (not allowed in some locations).

    Bookmark   April 29, 2012 at 2:44PM
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justalurker
    Bookmark   April 29, 2012 at 2:52PM
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crampon

Hey guys, thanks for the terminology correction re: air gap vs. high loop. I guess this is what I wanted to ask: is it acceptable to create a high loop for the dishwasher drain line by passing it through a high hole in the cabinet, or is it necessary to use a low hole in the cabinet and then use a strap to make the high loop?

    Bookmark   April 29, 2012 at 4:36PM
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justalurker

"... is it acceptable to create a high loop for the dishwasher drain line by passing it through a high hole in the cabinet, or is it necessary to use a low hole in the cabinet and then use a strap to make the high loop?"

AFAIK in areas where the high loop is permissible you start low then go high under the counter top and then down... hence the name high loop. Starting high then going down would not achieve the same thing as a high loop. I defer to those licensed plumbers on the forum for the final word.

Air gap may be required in some localities or not and high loop may be permissible in some localities or not. It isn't what you want to do or what is easier or more convenient or what someone tells you is OK.

If you want to do it right (according to local code) then check with a local plumbing inspector or look it up in the governing plumbing code yourself.

    Bookmark   April 29, 2012 at 5:16PM
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crampon

Hey guys, thanks for the terminology correction re: air gap vs. high loop. I guess this is what I wanted to ask: is it acceptable to create a high loop for the dishwasher drain line by passing it through a high hole in the cabinet, or is it necessary to use a low hole in the cabinet and then use a strap to make the high loop?

    Bookmark   April 30, 2012 at 1:03AM
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justalurker

How to correctly do a high loop is one thing.

The important question is whether the high loop or an air gap is required by your local plumbing authority and not what is pictured in generic dishwasher installation guides.

    Bookmark   April 30, 2012 at 1:40AM
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davidro1

Crampon,

yes.

The answer to your question is Yes.

    Bookmark   April 30, 2012 at 4:49AM
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brickeyee

"Couldn't I get the same effect without the strapping step by putting the hole for the drain hose at the top of the sink cabinet? Is there a reason why I shouldn't do that?"

Only if you want water spraying all over every time the DW pumps out.

It comes out with a decent amount of force, and a hole in the drain line will spray water all over.

    Bookmark   April 30, 2012 at 10:52AM
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asolo

"The important question is whether the high loop or an air gap is required by your local plumbing authority...."

Either way is easy. Learn your local requirement and do it right.

@brickeye....OP wasn't suggesting poking a hole in the drain line. Asking only about creating a hole high up under the cabinet to thread it through. That would make a "high loop" configuration.....if it's high enough.

    Bookmark   April 30, 2012 at 12:16PM
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weedmeister

Check your unit. The 'high loop' may already be part of the dw. That is, the drain hose runs from the bottom of the machine to the top (usually on one side or the back) and then back down again.

    Bookmark   April 30, 2012 at 3:34PM
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brickeyee

Do not confuse inlet protection for drain protection.

Your AHJ will not.

    Bookmark   May 3, 2012 at 9:06AM
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lazypup

First off, ALL CODES require a DW drain line to have a high loop. The exception to the rule is the case of commercial DW that discharge from the bottom of the machine into a floor receptor.

The UPC & many local codes require an "Air Gap" at the top of the high loop.

It does not matter how many loops, valves, backflow preventers or other doo dads that may be built into the dishwasher, the line is still required to have a high loop.

Drilling a hole through the top section of the cabinet as suggest by Crampon is fine, provided that hole is as high as you can get it in the cabinet. In fact, a hole in the cabinet wall would be preferred because it negates the possiblity of a wire hanger coming loose and dropping the line.

    Bookmark   May 7, 2012 at 3:41PM
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