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Your thoughts on an Air Admittance Valve (AAV)?

Posted by dcfixerupper (My Page) on
Thu, Jan 28, 10 at 8:27

My contractor installed an air admittance valve (AAV) for the main sink and dishwasher in my kitchen b/c we've moved the main sink to an area where there's only a half wall and is open to the family room on the other side. It's not an island - but for the purposes of this discussion, it's the same as an island configuration.

The closest vent stacks are quite a bit away and require a lot of breaking through floors and concrete. My contractor insists that AAV is the way to go and it's rated for 20 years. What do you guys think? We are located in Maryland - and I tried to look this up for plumbing code and can't tell.


Follow-Up Postings:

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RE: Your thoughts on an Air Admittance Valve (AAV)?

Does your house have a second floor? Answer this first even if you don't know yet why this question is being asked; it will be apparent to you later.


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RE: Your thoughts on an Air Admittance Valve (AAV)?

Yes, there is a floor above this area and we can't vent up through/near this sink area.


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RE: Your thoughts on an Air Admittance Valve (AAV)?

Even if it was easy to cut through the floor that would not be an option because code prohibits a horizontal run in a vent line until the vent reaches and elevation at least 6" higher than the highest fixture served by that vent.

If you code permits the use of AAV's that is without question the simplest and cheapest method, otherwise you would have to install an island loop vent.


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RE: Your thoughts on an Air Admittance Valve (AAV)?

AAVs handle negative pressure well, but not positive pressure. If a house has a second floor, positive pressure happens often. AAVs eventually leak or stop working, and whether it's in 15 or in 50 years is not the point. These reasons explain why they are sometimes banned, and sometimes allowed, depending on the code / authority having jurisdiction. In other words, you are fine for now because it's new, and and at some point down the line things may not be fine.-- hope this helps.


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RE: Your thoughts on an Air Admittance Valve (AAV)?

davidrol - I'm also considering having my plumber use AAV's instead of venting vertically through the roof because we have an attic that is usable living space above and I don't want the venting running through that. My question is when "at some point down the line things may not be fine" what exactly does that mean? Is it as simple as replacing the AAV ($30-40ish) or is there some additional work/potential problems that I'm overlooking?


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RE: Your thoughts on an Air Admittance Valve (AAV)?

Does she or doesn't she? Only her plumber knows for sure.

Do you have the room for a vent? Do you have the distances that require a vent, or is an AAV an option? Only her plumber knows for sure. The distances (lengths) permissible for "arms" (drain pipes without vents) depend on the slope of the pipe and the distance from the closest vent. You may or may not need a vent, and your local codes may or may not allow an AAV.

Talk to your plumber.

I cannot try to describe long term problems in detail. Venting removes gases, or more accurately, it isolates you from gases. These gases can be odorless and can sometimes kill. What exactly that means, hmm.

Hth.

Here is a link that might be useful: basement-venting (oldnorskie)


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RE: Your thoughts on an Air Admittance Valve (AAV)?

"My question is when "at some point down the line things may not be fine" what exactly does that mean? Is it as simple as replacing the AAV ($30-40ish) or is there some additional work/potential problems that I'm overlooking?"

We're required to make AAV's accessible, meaning they can't be buried in a framing never to be seen again.

Probably the most common sign of AAV failure that I see is a faint septic odor, usually due to the flapper valve losing it's flexibility and not sealing/seating properly. If the valve sticks in the sealed position and stops admitting air, then you can get different "non-venting" indications.

Regardless, if it's the AAV causing problems, the repair is easy. Unscrew the old AAV, dope up the threads on the new one, and thread the new valve on the existing stub. It's an easy DIY repair. $20-$30 for a new valve and five minutes to swap out.

Studor generally warrants their valves, so if one does actually develop a bad seal due to material failure, they'll send you a replacement for free.


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RE: Your thoughts on an Air Admittance Valve (AAV)?

Mongoct - Your response was exactly the clarification I was looking for. Sounds like when they do fail, the fix is relatively easy. Thanks for the explanation!


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