Tight house and “cheater vents” (AAVs)
jadziedzic
| Posted in General Questions on
OK, this is admittedly most likely a dumb question, but is there a reason to NOT use “cheater vents” (Air Admittance Valves) in a “tight” house with meticulous air sealing? I don’t particularly like the concept of anything other than an atmospheric vent, but does air tightness of a house have any impact on these mechanical marvels?
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Replies
Are you worried the AAV won't work in a tight house, or
are you worried about a regular vent in a tight house?
If the latter, there should be no direct air transfer from the house to the vent, because all drains in the house should have ptraps filled with water that block air transfer both ways - air from your house can't escape up the vent, and air in the sanitary line that contains sewer gases can't get into your house.
I'm guessing here, but I can't imagine the little slug of air that an AAV admits into the waste pipe from the interior of the house does much to mess with pressure balances in a significant way. Think of all the other ways pressure can become significantly more imbalanced. It just doesn't seem like enough volume of air.
There's no way even a very tight house will be tight enough to be a problem for the proper operation of an AAV. Even a very tight house will still leak a little bit of air, and an AAV needs only a VERY small amount of air (relatively) to function.
I'm not a huge fan of AAVs though, and only consider them in places where there is no other option. Always try to put in a "regular" vent to the outdoors if at all possible.
Bill
I can imagine a scenario in a very tight house that is not pressure-balanced with the exterior causing trouble with AAVs and plumbing traps, if the house is airtight and has exhaust-only ventilation, range hood, and dryer all running at the same time. But in that case you would have other problems as well. With a balanced ventilation system and makeup air for the range hood (and preferably for the dryer as well) you won't have any trouble.
I agree that AAVs should not be a problem, even in a tight house. Just make sure that you are installing AAVs, not mechanical vents. AAVs are OK in residential construction but mechanical vents are not.
Thanks for the replies. The AAV would be used in an island (kitchen) sink application, and I would make sure the plumber installs it in a manner that it can be replaced if it fails. There are a couple of other ways to vent that sink (island loop or combination waste and vent), but I'll probably let this one slide.
The house will have a balanced ventilation system with a separate makeup air source that can be triggered by the range hood and a (future) vented dryer. We're going to start with a heat pump dryer and see if my wife can get used to the smaller size. With only the two of us it shouldn't be an issue, but I will have a route for a future dryer exhaust vent if the boss says to switch to a vented dryer.
jadziedzic,
For island AAV installations, which are usually up in inaccessible corners of the cabinet next to the sink, I like to include a rubber coupling on the stack to make replacement easy.
When you turn on a faucet does it pressurize the house?
A tiny bit. So when you drain water does it depressurize the house?
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