# Air Admittance Valve question ......



## Vermonster

Hi - I'm doing a remodel for a client's basement bathroom. I am just replacing the vanity and shower stall with new items. They are next to each other. All drain pipes are in concrete, but I looks like the sink and shower drain run straight into the main drain pipe ... under concrete so I'm just guessing. I don't see a vent pipe anywhere for the sink and/or shower. There is only one vent pipe on the floor above floor.

I'm done with the upgrade, now the shower won't drain, the sink drain causes the shower to back up and gurgle like crazy. I assume that's because there is no vent pipe?

Since the drain pipes are under concrete I can't add a vent. But will a Air Admittance valve work? If I put one on the sink drain will that also help the shower drain?

Thanks for any advice .........


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## Double-A

fsteyer said:


> Hi - I'm doing a remodel for a client's basement bathroom. I am just replacing the vanity and shower stall with new items. They are next to each other. All drain pipes are in concrete, but I looks like the sink and shower drain run straight into the main drain pipe ... under concrete so I'm just guessing. I don't see a vent pipe anywhere for the sink and/or shower. There is only one vent pipe on the floor above floor.
> 
> I'm done with the upgrade, now the shower won't drain, the sink drain causes the shower to back up and gurgle like crazy. I assume that's because there is no vent pipe?
> 
> Since the drain pipes are under concrete I can't add a vent. But will a Air Admittance valve work? If I put one on the sink drain will that also help the shower drain?
> 
> Thanks for any advice .........


No vent? Did you tear down to the studs on this job? Did the shower gurgle before? Unless this job originally wasn't done by a plumber, I can't imagine why there isn't a vent.

You need to check with your AHJ. Just tossing an air admittance valve on in Arkansas is against code. State has limited approval of one brand and design only and requires Plumbing Engineer to design and draw up the installation and for those plans to be submitted for State approval.


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## Mike Finley

Double-A said:


> No vent? Did you tear down to the studs on this job? Did the shower gurgle before? Unless this job originally wasn't done by a plumber, I can't imagine why there isn't a vent.
> 
> You need to check with your AHJ. Just tossing an air admittance valve on in Arkansas is against code. State has limited approval of one brand and design only and requires Plumbing Engineer to design and draw up the installation and for those plans to be submitted for State approval.


Damn, they love the AAVs out here, at least in my home county, they don't put you through any of that.


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## Double-A

You haven't lived until you're heard an AAV 'fart' during a 20 min shower. I don't care for them at all. Nothing is as maintenance free and simple as a vent.


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## Vermonster

thanks ... in remodelling many things are not up to snuff. This job was definitely not done originally by a plumber ( or electrician). I did tear down to the studs and didn't see any vent. But since it has been a "functional" bathroom I didn't pay much attention to it then. .. it's just that the new shower drained fine before I hooked the sink (and p trap) up again. I figure that the sink drain acted as a vent until I "cut it off" with the trap. What do you think?
thanks again .........


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## Tom R

I've run into this on several occasions, - - basements 'set up' for future bathrooms. 

I've never yet seen the vent run in advance, though, - - appears they (correctly) figure no one will ever notice until it's time to do the job.

You're probably right about the trap 'blocking' the air, - - but you do need to install either the AAV or a 'real' vent. Sometimes a customer will prefer it (yuck!) to run 'outside' the house to save on some of the expense. As far as whether or not an AAV is permitted in your area, - - I'm guessing 'code' doesn't matter, - - or you'd have already had to show your venting on the plan.


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## Vermonster

Hi-
I installed the AAV under the sink, no change. There is even water in the standing drain pipe of the sink. So I figured it had to be a clogged drain. But I ran a snake and there was no obstruction I could feel. Plus the snake head was clean when I pulled it out.

So I used a plunger on the shower drain. It popped air and water in the sink and made the AAV pop. I saw some small particles come up and eventually the water drained. But still slowly. Could there be a clog I cant feel and lets the snake through? If so what can I use to unclog the pipes?

Thanks .......


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## Tom R

I would think your AAV has to be installed at least 6" above the rim-line of your sink.

But I'm a carpenter, - - and have never actually even used an AAV . . . 

Someone else??


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## Double-A

If the shower is downstream from the lav, then run your snake down the shower drain and keep it spinning the whole time. It might be that construction debris along with old hair has it clogged. 

The placement of the AAV is dependant on the manufacturer. Some can be placed as a 'weir crown vent' as you have it, some cannot. I prefer to not use them, but when forced, I will run a 'vent' above the flood rim of the fixtures served to keep it clean of debris from clogs.


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## Vermonster

thanks for the "declogging" advise.
I installed a Studor Redi-vent. The instruction call for 4" above the return pipe paste the trap. Plenty of room under a vanity.
Although in my case I don't think it did any good. It got to be a clog in the pipe.

thanks ....


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## Vermonster

Here are some pics of the setup .... as you can see I added a clean-out to the drain to make things a bit easier.
Here's whats happening now: the toilet (closest to the main) never had and has a problem and flushes just fine. The sink drains fine as well since I installed the AAV.
The shower is my problem. It drains VERY slowly until I open the plug on my clean-out. Then I have a nice vortex and the water runs off just fine. When I add the sink to it the shower backs up again. Also when I open the clean-out plug I can hear the air rushing in. Could it be that my AAV is not working? Or co8uld it STILL be a clog???
Here's a pic of the setup ... sorry for the quality. The AAV is sitting 6" above the drain return.









Thanks again.


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## mdshunk

What size is that AAV? They come in lots of sizes. Some will vent one fixture only. You're trying to use one as a circuit vent, and it's likely undersized.


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## Tom R

Seems to me, for one thing, I think you essentially have an S-trap, because your trap arm is so short, - - not sure if that's what's causing the problem though.

The other thing is, - - seems your AAV would work better if it was 'directly' above your vertical drain line.

Maybe the picture is deceiving, - - but it almost looks like your trap arm is pitched 'up-hill'.

Maybe if nothing else, - - try extending the AAV up and out of where you've got your cleanout, - - what limited venting you have now doesn't like making any extra turns.

I'm taking for granted you have no clogs.


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## Double-A

You have created an s-trap. Cut the elbow off above the clean out, extend that pipe up above the level of the sink 6" or more, put your AAV there. 

Where the elbow was, put in a sanitary tee fitting, and run your sink waste into that. 

If you can, just skip the AAV and run that line up and out the roof, or tie it into another vent. 

As far as the shower goes, its pushing air ahead of it for some reason, and needs a larger vent to work. When there is positive pressure on the system, the AAV will close. That is why the shower drains when you open the clean out. 

If you cover the drain in the shower with a cloth and flood the pan slightly, remove the clean out plug and put a piece of toilet paper over the hole, then let the water in the shower pan go, I think you'll find its being blown off the clean out, and not being sucked into the hole. 

Vents work both ways, to relieve pressure and to break vacuum. That is why an AAV is a silly idea and will never be as good as a vent.


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## Double-A

Tom R said:


> Maybe if nothing else, - - try extending the AAV up and out of where you've got your cleanout


Please don't do that. Leave the clean out in place if you can. You will need it one day. There is no way to clear the bigger WC line downstream if you remove the clean out without pulling the WC.

Just cut out the 1/4 bend and put a sanitary tee in its place, re size the AAV for both the lav and the shower, not just the lav and your problem might go away. 

If it doesn't the only thing that will solve this is to bust the floor and take the rise out of the branch line for the shower and/or run it in 2" as it should have been (no 1-1/2" traps under the slab per most model codes) or install a proper vent. 

From what I'm hearing, only a proper vent is gonna fix this. Vacuum breakers and AAVs ain't gonna cut it.


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## Vermonster

mdshunk said:


> What size is that AAV? They come in lots of sizes. Some will vent one fixture only. You're trying to use one as a circuit vent, and it's likely undersized.


it's a 1 1/2" Redi_Vent ........ what size should I go to? ... and can the bigger size go on the 1 1/2" pipe?



mdshunk said:


> You have created an s-trap. Cut the elbow off above the clean out, extend that pipe up above the level of the sink 6" or more, put your AAV there.


... I never understood what the difference is if the drain pipe runs vertical down _inside _or _outside _a wall. In this case it was in concrete so I didn't want to move it. I can't extend the pipe 6" above the sink level without tearing the walls apart again which is the LAST thing I want to do. Remember, all I really did was install new fixtures.



mdshunk said:


> If you cover the drain in the shower with a cloth and flood the pan slightly, remove the clean out plug and put a piece of toilet paper over the hole, then let the water in the shower pan go, I think you'll find its being blown off the clean out, and not being sucked into the hole.
> 
> Vents work both ways, to relieve pressure and to break vacuum. That is why an AAV is a silly idea and will never be as good as a vent.


You are right about pushing the air. If that is the problem the ONLY solution would be a regular vent, correct?  :furious:   

I don't understand though WHY there is an air blockage to begin with? The main drain (which has a vent) is only 8 -10 feet down the line. And the sink (which is between the shower and main) drains fine. Seems that the air would push easily that distance, or not? Also, once the initial air is gone where is the new air coming from?


If I read all this advice correctly my next step is to put on a larger AAV and see what happens (and hope), right?


Thanks for all the feedback ......


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## mdshunk

fsteyer said:


> If I read all this advice correctly my next step is to put on a larger AAV and see what happens (and hope), right?


Nope. Apparently you read all the advice given, and that's what you hoped it would say. An AAV, regardless of size, will only aspirate, so that won't solve your problem. It's looking like you have an issue with expiration also, and only a genuine vent will solve that.


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## Vermonster

thanks ..... but as I said, the max distance is 10 feet from the main (which has a vent). Wouldn't the air easily make it that short a distance?


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## Tom R

Double-A said:


> Please don't do that. Leave the clean out in place if you can. You will need it one day. There is no way to clear the bigger WC line downstream if you remove the clean out without pulling the WC.



I meant as a 'test', - - but you're right, - - thanks for the clarification.

Seems easier to me to do a test first, - - rather than start cutting and re-fitting, - - possibly for nothing. 

As I also stated, - - the AAV would work best installed directly above the vertical drain line.


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## Double-A

fsteyer said:


> You are right about pushing the air. If that is the problem the ONLY solution would be a regular vent, correct?  :furious:
> 
> I don't understand though WHY there is an air blockage to begin with? The main drain (which has a vent) is only 8 -10 feet down the line. And the sink (which is between the shower and main) drains fine. Seems that the air would push easily that distance, or not? Also, once the initial air is gone where is the new air coming from?


You have a belly in the pipe downstream from the lavatory, or the shower waste line is rising to the horizontal waste line that serves the lavatory. 

Sanitary plumbing systems are designed to run at 60% maximum capacity. This is to allow for an air space over the top of the liquid in the pipe on a horizontal run. Air must be free to move in both directions. This is why you have a restriction of 'grade' on a pipe. You don't want too much fall.

Some think that the liquids will run off and leave the solids, but the real reason is that every waste line is also a vent to a certain extent.

At this point, the only thing you can do to correct this problem is bust the slab or find a way to take that vent out the roof or tie it into the one that is 8-10 feet away. It must rise 6" above the flood rim of the highest fixture served (lavatory) before offsetting (turning).


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## Double-A

Tom R said:


> I meant as a 'test', - - but you're right, - - thanks for the clarification.
> 
> Seems easier to me to do a test first, - - rather than start cutting and re-fitting, - - possibly for nothing.
> 
> As I also stated, - - the AAV would work best installed directly above the vertical drain line.


I can roll with that, but when he said the shower drains well with the clean out plug open, I knew it was because the shower was pushing air ahead of it (99.90% sure), and that you can move that AAV around all day long and it still will not work. I had him test to convince himself this was the case, otherwise, he has a grossly undersized (highly unlikely, as the smallest you can get is 1-1/2") or defective AAV (more likely).


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