What About Vent Caps?

Forry

I've seen vent caps used instead of a real vent in a situation where a sink is installed in an island. These are basically a check valve that allows air to enter the drain system instead of actually venting out the roof... do these work? are they code? in what situations can they be used? how are they meant to be installed?
Thanks for any help...

rex

aav...air admitance valve....i question how well they work but they are code in michigan...in michigan on residental only one roof penitration is required the rest of the fixture groups can be vented with aav's...ive never done it that way but i see it all the time....if your using one under a cabinet you need a minimum of a 4 inch nipple out the top of the T

Forry

Hmmm... helpful, but more info would be good. Does this thing just let the drain flow well? What good does it do?

JPF

Your talking Studor vent yea?? See them on a few jobs down here in Fla, but not all......just allows air into the trap during draining to prevent any air-locking i assume......don't know how often that would be an issue, since not all systems have them....i think it's like you said, for particular situations where your a bit of a run from a stack....i guess you could check this out http://www.studor.com/index2.htm

Forry

Perfect, thanks for the link. I think I get it now.

KillerToiletSpider

You'd have to check your local codes, they are illegal in Illinois. After time they also have a tendency to get stuck in the open position, allowing sewer gas into the building.

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A flush is better than a full house.

Forry

Sooo, sounds like not the best choice, but might work in a pinch eh...

KillerToiletSpider

I would never install one.

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A flush is better than a full house.

Forry

kay

reveivl

If you do use one, make sure that you can get at it in years to come to replace it, as the diaphragm will wear out.

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mdshunk

There's a development that I service that was constructed mostly in the mid to late 80's. The developer had the bright idea that he didn't want to see any roof penetrations. All the homes had a 3" AAV in the attic. When I go into the attics in these homes to do work, I can often get a little whiff of sewer. One home had the AAV obviously stuck open, since the smell in the attic almost made me want to puke. I sorta thought the whole house even had a hint of sewer smell. I notice that many homeowners have since then gone ahead and removed the whole house AAV and took the vent on out the roof as it should have been in the first place.

Forry

This is a kitchen peninsula with a possible, but difficult and expensive venting route. I get that a real vent is the right thing to do, just not sure yet if its the best thing in this case. It probably is. I'm pretty much convinced.

reveivl

You might be allowed to use a loop vent, or barometric vent. (Different terms for the same thing).

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Ron The Plumber

Here is the link that tells if studor vents are allowed for use in your area.

http://www.studor.com/approvals.htm

Forry

Guess I can't use it... What's a barometric (loop) vent?

mdshunk

Forry

Thanks MD, you're a wealth of knowledge. (or good with google).

mdshunk

Good with Google.

Actually, that's a pretty common plumbing detail. It's pretty much the only way I've ever seen an island done in new work. Most self-respecting plumbers won't use an AAV in new work. Remodel work is a different story. I suppose they can help you out of some jams. Lacking that option, this is what you do. It is important to get that return bend as high as possible. Up tight against the countertop, or up into the splash area is better if you've framed in a backsplash that you can hide it inside.

Forry

What does the extra height do? More air in the loop? That can't be it, or the length of the loop would matter...

mdshunk

You need to keep that return bend above the flood level of the sink, lest you flood your vent if you let a bunch of water out quick. There's code on this sort of stuff. If you can keep it smack up tight as you can go, then you're good.