Need advice on air admittance valve replacement

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Kezug

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I seem to have a failed AAV. At first, my drain line was blocked with crud. I cleaned all the crud and snaked into the wall. All is clear. However, while that fixed one issue, I still was unable to drain. I was flabbergasted and I finally buttoned up the pipe and removed the AAV and voila, the water drained. I was able to run the water and no more did the water back up. But once I put the AAV back, bam, no more drainage...or extremely slow drainage. The AAV, when removed seemed to still have a flapper working as I could feel it when I tipped it or shook it.

So, here is the AAV....I have no experience, thus here to ask those who do and/or are pro's...is there a specific replacement AAV I must adhere too or can I use any AAV that I can screw into the 1-1/2", 2" as stamped on my existing AAV?
I would prefer to get/replace with same exact, but unsure if thats attainable or maybe I dont since the damn thing is only 14 years old!

Here is my current
20220907_210333.jpg
 

Kezug

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Additional question. The AAV has a 20 DFU stamped on it. However, at Menards, Will this replacement unit from Menards WORK (says 20 DFU Branch/8 DFU Stack? I have no idea if this will be sufficient?

Oatey® Sure-Vent® Air Admittance Valve - 20 DFU Branch/8 DFU Stack

Model Number: 392305 Menards ® SKU: 6932960​


Here is a picture of the location for which it exists today. It is under the kitchen sink, there is a dishwasher feed tube as well.
All the plumbing here you see was done from the build of house, we are first home owners. Built since 2008, no issues.


20220907_211055.jpg
 

Reach4

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A blocked vent will not normally cause a problem draining. The AAVs job is to prevent trap siphoning, which in turn would allow odors in. In your case, the AAV may be perfectly good, but removing the AAV allows you to expel air. So what would cause this symptom? I would suspect a belly in the pipe past the wall.

https://terrylove.com/forums/index.php?threads/sink-water-not-draining-no-blockage.88030/ has a roughly comparable situation, and in #20 I try to illustrate a belly.
 

Kezug

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Thank you for the reply. Turns out, past the wall, in a drop down run to the mainline going out the house, the entirety of the pipe was clogged. This was not my house, I suspect they were putting food and/or grease down the line and eventually the entirety of the pipe was clogged. When I released the AAV from the pipe, the water drained but it just went up that pipe and I thought it was going down. It wasnt (as I wasnt running a ton of water in my "test"). Either way, the AAV was fine. The pipe is now cleaned, unclogged and all is free flowing perfectly fine.
 

wwhitney

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In your case, the AAV may be perfectly good, but removing the AAV allows you to expel air.
And you can distinguish between the two possibilities by putting a tissue over the open pipe with the AAV removed, and seeing if draining the sink causes the tissue to puff up or get sucked in (don't lose it).

Cheers, Wayne
 
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