To gap or not to gap?

MizLizzieNovember 17, 2012

In the process of replacing my kitchen faucet config and have been shopping for a Waterstone set up. I notice all their suites have air gaps. It's been many years since I had an air gap and really did not know what they were. Having now (somewhat!) educated myself here by reading threads, I wonder if it is advisable to have one.

Our state code apparently does not require it, and I've never had an issue with our "high loop" under the sink. We had first a Fridgidare DW I think, and now Bosch, but will be changing that out soon for possibly a Kitchenaid. I have only 4 holes drilled in my granite, and want to use them judiciously. Should I reserve one for an air gap to be safe, and be a good citizen? And does the necessity for an air gap vary with DW brands, or is it all a matter of the high loop under the sink?

No RO system in use. Still, I would hate to special order faucet configs and DWs that were incompatible. Many thanks.

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I am getting away with a high loop, though, my local authority requires an air gap. IMO, they do exactly the same function, and, mine has been in for 6 years with no problem. The hole where the old air gap was (so I could get my permit signed off) is now occupied by a soap dispenser.

An air gap or high loop is necessary for all models, I believe, and, most DW installation guides say that one of the two need to be used but to check with the local authorities (permitting agency/AHJ).

    Bookmark   November 18, 2012 at 1:22PM
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Hello Mizz,
Here in California where I live Air-gaps are code. I suggest you spend the $5-$10 & add one into your new DW install. They work great when properly installed & will help your new DW drain nicely. Good luck.

    Bookmark   November 18, 2012 at 9:21PM
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By the way, it just dawned on me about your possible new DW purchase. I recommend the "Whirlpool" brand of DWs. I have purchased 2 this year, (Grandmas house & Girlfriends house). They make some really nice units & very energy & water efficient. If you want the higher end model, I put a black one in at my Grandmas & its really sweet. You can hardly hear it running standing next to it. Here is a few links for you:[WDT790SAYB]-1003281/WDT790SAYB/

Go to page 10 to see the efficiency specs for the Whirlpool models, very impressive on the water usage:

    Bookmark   November 18, 2012 at 9:58PM
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Thanks, guys. Air gaps are not code here, but it does strike me as safer than counting on a hose. I will check out the Whirlpool DWs. Thanks.

    Bookmark   November 19, 2012 at 8:15AM
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The air gap is hooked up with hoses.

At least some places have dropped the requirement for air gaps in residential DW installations.

They always have been over kill.

    Bookmark   November 19, 2012 at 11:51AM
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I agree with Brickey. If one were to compare a high loop to a air gap with the understanding what the setup is to address, the difference between the air gap and high loop is about 2" of additional raise - that is insignificant.

I live in California also, but, that didn't stop me from getting my permit signed off and then an install of a soap dispenser in the air gap's place and adding a high loop.

Just me...

    Bookmark   November 19, 2012 at 12:43PM
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"If one were to compare a high loop to a air gap with the understanding what the setup is to address, the difference between the air gap and high loop is about 2" of additional raise - that is insignificant"

Hardly the difference and hardly insignificant. You don't seem to understand what an air gap is and how it works in a DW installation.

A high loop is a closed loop that can be overcome by backflow from the drain sufficient to overcome the height of the loop and then cross-contamination of the potable water can occur.

An air gap is exactly that. Backflow from drain CAN NOT overcome the air gap. Backflow from drain will run into the sink from the air gap housing because the air gap is open to atmosphere and cross-contamination of the potable water will not occur.

Regardless of how many choose the high loop and how many never had a problem with a high loop the air gap is real protection from cross-contamination and the high loop is not.

    Bookmark   November 19, 2012 at 1:22PM
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Lurker has spent the time to explain the function/purpose of the Air-gap in detail. I know a guy that is a health inspector that told me that they will shut-down a restaurant when they discover that a DW does not have an Air-gap properly installed. They will reopen when it is installed; imagine the cost of that over-site in a large restaurant?

They have made & sold millions upon millions of these little devices, there is a reason why.

    Bookmark   November 19, 2012 at 5:23PM
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Justa, I BOTH know what it is and what it does. It is overkill, just like Brickey stated. Nice picture, though!! :)

    Bookmark   November 19, 2012 at 5:41PM
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So tjdabomb your position is that you'll take the chance of drinking your sewage and that's fine with me but I draw the line when someone is irresponsible in recommending that others take that risk along with you.

I defend your right to be as reckless and stupid with your own health and safety as you like. So you and brickeyee keep your sewage at your lips and I'll keep my sewage an air gap away.

I'm confident that even in those locales where the plumbing code does not require an air gap on a DW and allows a high loop no plumbing inspector would make a plumber remove an air gap if they installed one.

As a side note, softener installs require an air gap on the drain line in most plumbing codes and a while back a buddy of a buddy had a sewage backup and the entire plumbing system was contaminated because the DIY homeowner installed a mail order softener and didn't know what an air gap was so he didn't install one. The entire family got sick and it cost the homeowner considerable discomfort and a fair amount of money to sort that out.

    Bookmark   November 19, 2012 at 6:12PM
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Hey Bomb,
Not sure what you do for a living but I see custom built multi-multi-million Dollar homes being built with Air-gaps installed in the kitchen for the DWs. Anything that protects you from bad bacteria that makes you sick does not sound like over-kill to me. I suggest you look-up how many contractors license specialties/classifications it takes for building in California, then how each trade gets trained (up to 6 years) & then retrained to keep up with the changes in technology, materials/building codes.

Your talkin out of school.

    Bookmark   November 19, 2012 at 7:08PM
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Wow. It's way more exciting over here on Plumbing Forum than on Kitchen Forum.

My only claim to cred here is that my late father was a pipe fitter. (Couldn't plumb worth a s**t though, now I think on it.) But I'd go with the air gap for sure. Then again, I live on the highest hill in town, and I bought flood insurance -- to protect my garage full of Volvos.

Yes, I embrace overkill.

Thank you all for sharing your not insignificant knowledge with a newbie. I actually understand what the blasted thing is now, too, which is saying something.

    Bookmark   November 19, 2012 at 9:34PM
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    Bookmark   November 19, 2012 at 10:09PM
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I am a plumber so maybe I can shed some light here;

Under the UPC you are required to have an air gap.

Under the IRC a high loop is permitted, but the problem here is that many DIY'ers and homeowners do not configure the high loop correctly to meet code spec.

It is not enough to just hang the drain hose up high somewhere in the cabinet. To meet code the drain line should be attached as high as possible immediately behind the DW, then the line should drop down to the base of the cabinet and run to the drain connection where it rises up to the final connection on a disposal inlet port or a DW inlet port on the sink tailpiece.

If you just drill a hole high in the cabinet wall between the sink cabinet & DW location then run the line up through the hole and straight down to the Disposal or inlet port that will not pass. The line MUSTcome down from the high loop to an elevation below the trap then return back up to final connection.

    Bookmark   November 20, 2012 at 8:46AM
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"cross-contamination of the potable water can occur. "

Bovine Scatology.
Every DW already has a built air gap on the supply side.

The unit will not hold enough water to submerge the water inlet.

Some very old units (especially portables) did not have a supply side air gap, but it was normally built into the adapter that clamped onto the faucet well above the flood level of the sink and proved both inlet and outlet protection.

And despite all the (likely) thousands of non-code complaint installations (no air gap or inadequate high-loop) no place has recorded issues beyond urban legend.

    Bookmark   November 20, 2012 at 10:22AM
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