Our double sink stopped draining. We called a plumber he came out and used an electric snake and said he hit snaked approx. 55 feet. Drain did empty but very slowly. Plumber said he was sure there was no longer an obstruction. He did tell us he felt we needed a mini-vent underneath the sink since it was not vented. Sink sits in a center island in kitchen. He put in mini-vent and it appeared to work well. Later that day the sink would drain but would back up. Then it would drain and you could hear it gurgle as it emptied. Tonight it backed up again and drained real slow. As soon as I unscrewed the mini-vent below the sink it emptied quickly. I left vent off and then I could run water as hard as it would go and the sink drained well. Put vent back in and it drained OK for only a while. What is up with all of this. Thanks, Bruce

He was correct to install a Studor or AAV but in this case, it failed. AAVs must be placed in an accessible area because they fail, just not as fast as this one but they do fail.

O.k. so I had the mini vent less and a day and it is bad? I have to buy another? One last question, could the vent be working against the Ptrap and that is why water is having a difficult time working through the Ptrap since the mini vent is on the other side of the vent? Thanks. Bruce

No, I'd call the plumber back and tell him HIS work failed.

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Originally Posted by brucef1

Our double sink stopped draining. We called a plumber he came out and used an electric snake and said he hit snaked approx. 55 feet. Drain did empty but very slowly. Plumber said he was sure there was no longer an obstruction. He did tell us he felt we needed a mini-vent underneath the sink since it was not vented. Sink sits in a center island in kitchen. He put in mini-vent and it appeared to work well. Later that day the sink would drain but would back up. Then it would drain and you could hear it gurgle as it emptied. Tonight it backed up again and drained real slow. As soon as I unscrewed the mini-vent below the sink it emptied quickly. I left vent off and then I could run water as hard as it would go and the sink drained well. Put vent back in and it drained OK for only a while. What is up with all of this. Thanks, Bruce

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Hey Bruce,

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the sink would drain but would back up. Then it would drain and you could hear it gurgle as it emptied

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And here we have "The Smoking Gun"! Your sink's venting through the trap because the AAV has failed. The plumber should come back and replace the AAV under warranty at no charge to you. Good luck. Tom

Just a side note. This is why you will never see me suggest an aav. They are prone to failure as they are mechanical. This is why many codes do not allow them. Nothing beats a true vent. However, in your case, since this is the only option for you, just have the plumber come back and put a new one in. Can you post a pic of the piping under your sink, and let us see how the aav was installed? If it was installed to low, it will fail over and over again.

Here is a picture of under the sink. Do you think the way it is set up could be causing a problem or is it strickly the mini-vent? As I have said if I leave it in but only half tighten it everything works fine. As soon as I start to tighten it in I lose my water flow out of the sinks. Thanks, Bruce

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Originally Posted by brucef1

Here is a picture of under the sink. Do you think the way it is set up could be causing a problem or is it strickly the mini-vent? As I have said if I leave it in but only half tighten it everything works fine. As soon as I start to tighten it in I lose my water flow out of the sinks. Thanks, Bruce

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Hey Bruce,

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As I have said if I leave it in but only half tighten it everything works fine. As soon as I start to tighten it in I lose my water flow out of the sinks.

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You just proved our case for us.
Call the plumber back. This should be replaced under warranty with no expense to you. Good luck, Tom

It is not 100% clear to me where than drain goes back by the rear wall of the cabinet. I see s few things that tell me a plumber did not do this original install starting with the bent rigid copper pipe coming up through the floor.

The bend copper pipe is actually for my exterior hose bib. There is a small handle in the picture that turns my hose bib off outside. As the min-vent enters the pvc pipe it goes left in the picture and then the plumbing goes directly down into the floor. The house is on a slab.

OK then, you need a AAV otherwise this would be an S trap which is not allowed in most locations. Call that plumber back and tell HIM to fix it.

Seems the vent should go up in the corner extended as high as possible, but I also have had problems with those vents.

I agree Img. The aav should be taken up either behind the sink or in the corner and placed as high as possible while still leaving room to unthread it. If the aav is to low, as it is in your pic, it will not suck in air as the water draining will create enough pressure to push up on the aav keeping it closed. Ideally the aav would be located above the highest water level in the sink, although that is impossible to do under the sink, so just get it up as high as possible. Now, all that being said, I would still stick with the other pros here and just have the plumber back to replace the aav. Then, if it still gives you issues, it needs to be raised.

I see another issue. The outlet under the sink does not appear to be GFI, which I believe is code around water fixtures like kitchens and bathrooms. It's an important safety feature worth spending $5 to remedy.

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Originally Posted by solarpv

I see another issue. The outlet under the sink does not appear to be GFI, which I believe is code around water fixtures like kitchens and bathrooms. It's an important safety feature worth spending $5 to remedy.

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If it is a dedicated circuit with a plug in device a GFCI is not required. Same as a refrigerator outlet.