Kitchen sink air problem?

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Clevjoe

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I have an odd problem with my kitchen sink and I'm completely stumped. Double kitchen sink with disposal backs up through both drains. There's no blockage! All the obvious stuff is clear...p trap, T, tail pieces. Ran snake 25' well into main 4" line. And has worked fine for years...all of the sudden. If it backs up, I remove AAV and water drain immediately but if I run it with AAV completely removed, still backs up? Seems like so kind of air trap or something? Any help would be great
 
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WorthFlorida

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A picture of under your kitchen sink maybe of help. Is the AAV above the flood level of the kitchen sink or as high as it can be? Does the drain turn down inside the wall or is it a horizontal run before going down into the main stack or basement? What type of pipe after the trap arm? Is it possible there is a dip or a rise in the drain pipe after the trap arm? A common drain issues that comes up on this forum, at times the trap arm (A) is higher than (B). Is this a fairly new home or was there a major remodel?

Have you tried a new AAV? From your description it seems everything is proper since it drained fine at one time. Any drain problems at other fixtures? Has the roof vent been checked for obstruction?


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FYI...AAV only allows air to enter the drain. Sometimes as a water column drains, it pushes on the the air (positive pressure) and a roof vent allows this so the air can escape. It is the reason that house plumbing must have at least one roof vent when using AAV's. I have AAV's on most sinks and I never have had a problem.
 

Clevjoe

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Everything is proper and was done by the builder in 2008. There has been no remodels and this has always worked fine until the other day. All other fixtures work fine. Would a new AAV change anything if it still backs up with no AAV?
 

WorthFlorida

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Does the backup only seem to be at the trap area and not further down? I would run a garden hose down the roof vent just to be sure that it is clear. I was asking only if you tried a new AAV, not to change it. When you stated the problem just started, there must be some kind of blockage since it is something that can change. Birds or squirrels can get stuck in a roof vent. Recently I had a squirrel stuck in one of my rain gutter down spots and the drain hole was quite small.
 

John Gayewski

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Have you tried lifting the flaps of the garbage disposal splash guard? Usually when you do that you'll see some air bubbles come up and it'll glug the water down.
 

Clevjoe

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To simplify the issue and eliminate any possibility of something with disposal or dishwasher drain, I ran a tail piece straight down to the trap and eliminated the 2nd sink for now
 

Jeff H Young

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more than one way to plumb a double sink and more than one way to mess it up. according to you its been plumbed this way for a dozen plus years. I can see no reason your aav is causing this. your experiment prooved its not a vent issue Of cource an open pipe under sink would not be smart except for the experiment.
No work has ever been done and issue been going on many years?
maybe pictures of under sink will help
 

Clevjoe

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There is no blockage in the stack. All other fixtures work fine and no slow or girgiling drains. This issue has been going on for 3 days, never problems in the past. Is it possible the trap can create a vacuum or lock prevent anything going through? I said earlier, if you let the water back up in the sinks and then unscrew the AAV, the water instantly drains. But if I ran the water again with the AAV still unscrewed, it backs up again. I don't know why the water releases when the AAV goes from tight to loose.
 

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Reach4

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There is no blockage in the stack. All other fixtures work fine and no slow or girgiling drains. This issue has been going on for 3 days, never problems in the past. Is it possible the trap can create a vacuum or lock prevent anything going through? I said earlier, if you let the water back up in the sinks and then unscrew the AAV, the water instantly drains. But if I ran the water again with the AAV still unscrewed, it backs up again. I don't know why the water releases when the AAV goes from tight to loose.
Nice looking installation.

See https://terrylove.com/forums/index....alves-exist-like-air-admittance-valves.95874/ including post #4. It tries to show how a deep belly can cause your symptom.
 
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