# Water back flows and leak from vent under kitchen sink



## kert (Jun 27, 2020)

Forgot to mention, the vent is a Durgo Sweden air admittance valve. Here is a picture looks like mine.


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## chandler48 (Jun 5, 2017)

Plumbers will chime in, but double trapping the sinks is a problem. You should have the trap after both sinks tie into a common drain across to the trap. Hang in their for their solutions.


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## kert (Jun 27, 2020)

Hi Larry,

Thank you for your reply! It was double trapping before and works fine for years. Here is the picture I took before the change. It was two 45 degree elbows at the bottom but now it is 90 degree elbow

Best!


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## XSleeper (Sep 23, 2007)

In addition, the biggest problem I see are the two elbows that should either be long sweeps or sanitary elbows.


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## rjniles (Feb 5, 2007)

Partial blockage downstream.

Sent from my Moto E (4) Plus using Tapatalk


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## MTN REMODEL LLC (Sep 11, 2010)

I'm with RJ....I think it's that simple...(not that a couple of sweeps verse the 90's is not a good idea.)


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## MTN REMODEL LLC (Sep 11, 2010)

Curiosity...at one time, was not an AAV vent required to be above the sink weir...??


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## dj3 (Apr 27, 2020)

While 2 traps are acceptable, one trap is better here. It will also save you space.
Your problem is in the two elbows.
If you re-do your drain with one trap, which goes straight down into the drain at the base with an AAV up on top, you will eliminate your problem.
If you still have water coming up the AAV, you may have a blocking under the floor.
Go to loveplumbingforum.com.


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## kert (Jun 27, 2020)

Thank you all! 

For the partial blockage, the downstream is very simple and it goes strait into my crawl space under the house. There, a PVC pipe directly goes to the city sewage lines. All pipes under the sink are new. it is hard to believe that I accidentally dropped something inside the pipe when I glued them, at least I hope I did not!


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## kert (Jun 27, 2020)

Hi Dj3, 

If I decided to go with 1 strap, will this design be acceptable? I will still have the vent on the top left and possible two 45 degree to replace the 90 degree elbow at the bottom.

Thank you!


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## Ghostmaker (Mar 2, 2013)

Your sink has a blockage and you need to replace your AAV. Once they leak they are garbage.


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## kert (Jun 27, 2020)

Ghostmaker said:


> Your sink has a blockage and you need to replace your AAV. Once they leak they are garbage.


Yep, I am heading to the store for a new one. Will give an update. 

It looks like someone else got the same issue before:
https://diy.stackexchange.com/questions/151849/should-a-brand-new-aav-be-able-to-leak-water


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## dj3 (Apr 27, 2020)

kert said:


> Hi Dj3,
> 
> If I decided to go with 1 strap, will this design be acceptable? I will still have the vent on the top left and possible two 45 degree to replace the 90 degree elbow at the bottom.
> 
> Thank you!


That's basically the idea, except you have to make it work in your situation, since your drain goes very close to the left sink drain. 
Use the ability to rotate the trap work for you. The AAV can have a couple of 45s so it can extend above the sink flange, and yes, get a new AAV.


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## u2slow (Feb 9, 2012)

rjniles said:


> Partial blockage downstream.


Agreed. I have nearly the same setup under the sink, and crawlspace connection.

The old 1.5" line snaked into the wall first, then down, and across into the 4" main. It became jammed due to almost no horizontal slope in the subfloor, at which point it also had too many bends to snake, so I abandoned it. Put in the under-sink vent and new 2" directly *through* the cabinet and subfloor to hit the same main line with a better slope. No issues since.


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## kert (Jun 27, 2020)

The more I look at it, the more I think the two 90 degree elbow at the bottom are the cause of the partial blockage downstream


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## u2slow (Feb 9, 2012)

kert said:


> The more I look at it, the more I think the two 90 degree elbow at the bottom are the cause of the partial blockage downstream


Also, what are running through the garbage disposal? Some material can pile up. I pulled a big wad of celery strings on one drain clearing attempt. Chop that stuff up first! :wink2:


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## kert (Jun 27, 2020)

LoL, life is full of surprise! :surprise:


u2slow said:


> Also, what are running through the garbage disposal? Some material can pile up. I pulled a big wad of celery strings on one drain clearing attempt. Chop that stuff up first! :wink2:


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## kert (Jun 27, 2020)

Updates:
1. I did run snake on the pipes
2. I did replace the AAV with a new better one named Studor mini
3. I did pour the Drano drainage unblocker into the sink and waited for 25 minutes, and pour a lot of hot water 

It seems now the backflow on the left sink still happens with the same test. The AAV leaks a tiny few drops only which is a lot of better than before. I think it is fair to conclude that the 90 degree elbow flow restriction is the cause. I will replace those with two 60 degree elbows when I have plenty time to have such "fun"! Thank you all for the help!


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## bruceb3 (May 5, 2020)

The line is partially clogged DOWNSTREAM of your new piping. Snake it and replace your AAV. We actually charge more to pipe the sinks in with separate traps. With separate traps, you are less likely to clog the tee on a twin waste. That tee has a divider in it that makes it more likely to clog. I would have used 2- 45's instead of the vent elbow at the floor of the cabinet, though.


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