Air Admittance Valve Under Kitchen Sink

Comments about AAV height in relation to drain height?

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Was it needed.?
Give us info on location and distance from the nearest plumbing vent.
Was this an island sink?

We can go from there.

Not an island sink. Distance to another vent should not matter in this case. It looks like lazy plumbing to me. A powder room was in an adjacent room less than 5 feet to the right.

My question about comments was more about position to drain height, I suppose I should have specified. The disposal outlet for the other sink side is the horizontal pipe.

Higher than the horizontal, I believe.

4 inches above the fixture drain.

That was what I thought as well, thank you.

First a HI isn’t a Code Inspection.

IRC P3114.4 Location
“Min 4 inches above the horz branch drain.”

Photo is cruddy, doen’t include the p-trap, so you don’t give the full info. So based on this info, is it ok? Guessing from the photo, it’s ok. If the AAV is downstream of the trap.

As to why it was used, no photo given, but betting there is a window above this sink. Just a guess. We need photos if you want to ask for good answers. :smiley:


IRC Definitions “Fixture Drain - The drain from the trap of the fixture to the junction of that drain with any other drain pipe.”

Now is the AAV min. 4" above the drain from the TRAP?


You are correct.

The fixture drain will be the trap arm, not the drainage outlet of the fixture as I had interpreted. Drainage outlet applies to loop vents, apparently not to AAVs.

Editing previous posts to remove the inaccurate comment.

The P-Trap outlet is visible at the bottom of the AAV, which is more than 4 inches below the AAV. What I gather from the posts: this application is then proper? What about the horizontal disposal outlet pipe?


Photos? Or do you want us to guess?


It is the only horizontal pipe visible in the photo. No guessing required. Click on the thumbnail to enlarge the photo.

There is no disposal in the photo so no distance reference. How far away is it? Does it slope propertly, is it leaking?

tom <Guessing>

Hi Tom,

The disposal is in the upstairs bathroom. :mrgreen:

No, seriously, it is a standard twin bowl kitchen sink. No leaks visible. Probably about 12 inches of pipe with a slight slope.

Sorry I only took one photo F.My.I.


12" < IRC 3201.6 limit (30"), so sounds ok?


P.S. what might be worth writing about is the (GUESSING) diswasher drain. It doesn’t appear routed high enough (GUESSING). :smiley:

Thanks Tom,

The DW drain was a separate issue.


I’m sure a lot of people will tell you, photos are your friend. I often regret not taking enough. I sometimes use the photos later to remember issues, and often to figure if I missed something.

Good luck,


I agree,

I did not think this needed alot of pics for my use. I thought the AAV seemed a bit low in relation to the sink traps but you cleared that up. Thanks.


FYI, I take the time to explain to my client problems associated with AAV’s. If they fail open, you get sewer gas into the home, or even water coming out of them if a clog interferes with draining.