This valve, I'm pretty sure it's an AAV valve,is now hidden inside the wall. I intend to have the contractor re-open the wall, ( it's only sheetrock) to address this. There was no way to tie into the existing conventional vent pipe

Does it need to be mounted so high? This is for a basement kitchen sink which will have a dishwasher using the same drain. The problem is I intend to install a backsplash over it and I suspect tiling around a panel might not look so good.

Is an access panel mandatory? I certainly don't want to break into walls when it fails down the line.

IMPORTANT- Is a better option to close or somehow cap off the current AAV valve and install a new one under the sink cabinet? I know higher is better, Since this sink is the closest fixture draining out into the street side, I'm not sure if that was influencing the decision for existing mounting height.

Also, is it acceptable to add a second AAV valve under the sink while leaving the original one buried in the wall or must that original one be removed and capped off? I know this is probably not correct but I just want to know how to respond in case the contractor throws that option my way.

If the best option is to leave it at the existing location, put an access panel then backsplash around it I'm okay with that.

Lastly, would you mind taking a look at the other photos to check if the other plumbing appears to be done correctly?
There is also another AAV for the washing machine where doing a panel wouldn't be a problem, and a close up picture of the kitchen sink valve.

Thank you all so much. Much respect to all you plumbers!!

i don't like much that was done.. best thing to do is call the local plumbing inspector.

Thanks Packy,
Could you please elaborate on what you dont like? Are there any major red flags that must be rectified?

How does the bathroom plumbing look?

Please advise and thank you again

access to an AAV is necessary since it is a mechanical device and it may fail one day and needs replacement.

It needs to be mounted as high as practical if you put it inside the sink cabinet it will most likely be installed with your faucet, the disposer connection, the DW connection, the faucet supply hoses, and the sink in the way in getting it higher but it is done at times. What is the other side of the wall, is it an interior partition wall? If so the access panel can be on the opposite side.

the basic design of the rough plumbing seems OK to me. the AAV's hidden behind the wall is not good nor is it to code.
AAV's can be installed under a sink cabinet, right out in the open.
studor makes an aav with its own wall box and cover.
[www.amazon.com]

Thanks guys,

The other side is the neighbor's side of the party wall.

Going higher would have to go behind an upper wall mounted cabinet with a cut out and it would be close to the ceiling joists with limited air flow. Not sure what you all think about that option.


As for the washing machine vent would it be better to make some kind of Y connection to bring it up and out from the wall more "in the open" or is it okay as is, with an access panel, in between the uninsulated studs?



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If the other side of the wall or sink cabinet is not an option, you can also I believe extend the valve higher until it is behind the top cabinet so the access can be hidden behind cabinet doors. I am not a pro so wait for them to comment.

higher is not better with an aav. manufacturer recommendation is only 4 inches higher than the trap it serves.
as for air needed, remember they work fine under a bathroom vanity or under a kitchen sink cabinet.
BTW, i'm from mass and we need a special letter from the vatican if we need to use aav's. they are illegal here.

In picture number three, there's some blue tape plugging up what appears to be a horizontal tee with the branch for the drain outlet and the vent coming in from the back side of the tee?

Hi Steve!!

Yes, I think that blue tape is covering the trap where the bathroom sink will be installed so it will be removed shortly.

So I spoke to the contractor and he said he did not want to put the AAV valve under the sink (pic 1) because he is afraid if ever a main line clogs and overflows from it.

He also said the 2 AAV valves on the wash machine and sink are "extra help" with venting and that this sink still gets some vent power across from the bathroom vent, and he said all the lines shown are tied into that underground.


Soooo, with all this great information and I know Packy said higher is not always better with an AAV valve, at this point, I am thinking the best option is to RAISE the valve in pic 1 another few feet, still behind the sheetrock in an uninsulated cavity, nearer the ceiling, and put an access panel inside the cabinet.

My thinking is that the contractor does not want to put it under the sink and we can't leave it as is because it will be ugly tying an access panel into backsplash.

Do you guys think my plan is okay? Will the valve still "work" up high. I really appreciate this help!

If the main line plugs up and floods out of the under sink aav, if you put the aav up high then the sink will fill up and flood over.

your contractor is full of crap.
if there is a main lime backup the water will overflow the tub or shower before it come out under the sink. besides that the aav has a sealing rubber gasket to prevent that. if water comes
out that is a sign of a defective aav and sewer gas has been leaking into your home all along.
there is no code on this planet that says a vent on the other side of the room will "HELP" vent a trap across from it.
if you don't think you are getting adequate advice, get the plumbing inspector involved.

Thanks Packy,
I understand your point.
I think a concern the contractor raised, or as I interpret it is that IF the valve failed while under the sink
Water would flow out in the event of a concurrent main line clog, however if that scenario occured with the valve in its current location, it would flow into the sink and there would be an opportunity to collect inside the sink not causing a spill onto the floor.

Would it still “ work” if I mounted it up high near the ceiling behind the wall and cabinet. I realize it might not be an ideal as lower by the sink but I need to access it somewhere.

Also if the valve were to fail up high near the ceiling, or where it is now, are you saying the sewer gas would emit due to the trap being sucked dry or would the main vent prevent that from happening? The main vent is about 10 feet parallel to this.

Im just trying to do this in a safe, reasonable way that will allow access to the vent and will work



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if the valve fails in the open position it will help the trap maintain its seal. the smell would come from the valve.
if the valve fails in the close position then there is no protection from the trap being syphoned. the smell would come from the trap.

I am also of the opinion that having two AAVs is counterproductive and confusing. If you have one AAV and it fails you can either smell it because it's stuck open, or if it stuck close it will no longer prevent siphoning and you will smell it from having a dry trap. Now if you have two one inside wall and one under sink if one fails it will mask the problem the other one still working, you may replace the working one and the problem perists. I don't think having two help at all.

As for the one inside a wall vs under the sink. Yes if it's working the water should not spill into your sink cabinet it will go up into your sink if the blockage is local before the branch merges into the main line. Since you are in the basement, is there a floor drain there? It will first show up in floor drains, tubs and showers. Personally I prefer the AAV inside the wall with an access door, instead of under the kitchen sink for two reasons. First, a kitchen cabinet is always congested. You have the disposer, the dishwasher hose coiled up there, you have sink faucet hoses and valves, icemaker line, then you add an AAV to all that, and it makes it more difficult to service the valves or the faucet in that tight space. Add to that nowadays these pullout kitchen faucet with a hose on the underside usually with a heavy donut to weigh it down, and when you pull on it it's stuck because the donut is caught on a valve handle or twisted between the AAV and another hose. So when I can I put the AAV inside the wall. Secondly by putting it inside the wall, if one day you decide to vent it atmospherically, you just extend it up without the need to cut any walls just need to drill out the hole in the top plate and out the attic.

The down side of putting it into the wall especially behind a cabinet is what you will be storing in that cabinet. If the AAV fails and you smell sewer gas, you open up the cabinet door and smell something, than open the access door the smell hits you in the face, what are you storing in that cabinet if it's cereal or cookies or whatever they may have been soaking in the sewer gas for days.

@new2plum, amateurs like us shouldn't debate with Packy. I think the answers you were looking for were, "manufacturer recommendation is only 4 inches higher than the trap it serves" and "your contractor is full of crap."

LOL, Dave. Don't beat me up but that was really funny summary.

I am a beginner, not even in an amateur league! I don't doubt Packy for one second and I appreciate all the expertise here. I may be overly inclusive with this and amazed with everyone's generosity of time.


So its a farmer sink to be installed. Probably going for a 20" or 24" wide I don't have the exact dimensions but I have a bit bigger one in an upstairs kitchen, which is 30" wide x 9" deep( which vents conventionally) and to get 4-6 inches above trap is kind of tight, and the donut weight thingy is in the way a bit too. SEEMS like my BEST option is to "aim" nearer the wall opening, before the p trap for the 4".

As a last resort, is it acceptable to mount a horizontal pipe, then vertical off the branch coming from the wall to get more space under the sink if needed and install the AAV on the side of the sink or does it have to be right on the pipe before the p trap?

For the dishwasher is an "AIR GAP" required? Anything else I should look out for when they put it in?

Trying to do everything I can to get this installed under the sink. Final alternate option is high near ceiling with panel, no way leaving it where it is now in the wall. Do you guys think the "EverFlow Provent 1-1/2 " valve is good enough in quality?



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DW airgap requirement will be a state/local code issue for where the house is. I shift kitchen sink drain and water supplies far off center to provide clearance for pullout hose.

horizontal pipe from the wall outlet to a vertical is only acceptable if the aav is on the top of that vertical. a sanitary tee at the top would allow the drain to come into the side of the tee and the aav come out of the top'

Thanks Packy!!


For my specific sink, any benefit in using one of these better "Studor" AAV valves since the "Everflow Supplies Provent" I have costs about $4.

Are these normally just hand tightened with anti-seize?





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i can't comment on which valve is better since i don't use them. they are illegal in mass..

as far as future replacement, a few wraps of teflon tape will seal the threads and allow for easy removal.

Studor is the leader of the pack.....

I used one in a half bath, and installed the AAV in the wall above the sink with an access panel, then hung the bathroom mirror over it. Under the sink wasn't an option because it was a pedestal sink.




Think about what the finished room will look like....you might run the AAV high up on the wall and hang a clock over the access panel, or a picture or something that hides the access panel. If you plan on having a microwave on the counter, consider putting the access panel behind that.

If you are adding the access panel to the tiled area of the backsplash, tile first and then install the panel and frame. You can also color-match a quart of pain to the tile and paint the access panel to make it less visible.

To Packy's point, an AAV can be installed as close as 4" above the trap it's protecting and going higher neither helps nor hurts how it functions. If it was me, I would put it under the sink.

Thanks for the replies.
Would removing then capping the AAV value off at the top, then moving the valve under the sink work or does the vertical vent pipe in pic 1 need to be cut down near to the height of the future p trap then capped before installing under sink



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