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Thread: AAV on shop utility sink

  1. #1
    DIY Junior Member Jfree's Avatar
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    Default AAV on shop utility sink

    Hi All,
    I have a deep basin utility sink in my detached shop. I just moved here and I suspect this drains to a dry well or daylight. When the snow melts, I will know for sure. There is no vent. There is a 2" Pvc drain coming up through the floor, offset about one foot from the center of the drain, which has a 1 1/2" trap on it. THe problem is this was draining very slowly. So I put a tee on the vertical and ran a riser up one foot and placed a trap vent on the top to let some air in. THis did not work, but when I unscrewed the spring loaded trap vent, lo and behold the water rushes out. I thought the trap vent might not draw air in easily enough, so I replaced it with an air admittance valve only to find that it does not work either. So when the top of the tee is open, pipe vented to open air, it does what a good drain pipe is supposed to do, it drains. When I put on trap vent or AAV, I am back where I started. Something I noticed, is that the vent pipe has positive pressure in it when water is draining which would cause the diaphram to close instead of opening. Do I need to shorten the riser? or Do AAVs only work in conjunction with vents to open air. and also I realize that this whole scenario isn't quite kosher. Any help would be greatly appreciated.

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    DIY Senior Member kreemoweet's Avatar
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    Default

    Just another example of the inadequacies of AAV's and "trap vents" (whatever that may be). Just leave
    the top of your vent riser open. Might want to run it outside or through the roof, or at least extend it
    at least as high as the rim of the sink.

  3. #3
    DIY Junior Member Jfree's Avatar
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    Default stumped

    Thank you for your reply, do you have any idea why this doesn't work, I am stumped. photo included this time.
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    Last edited by Jfree; 01-26-2010 at 04:48 PM.

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    Forum Admin, Expert Plumber Terry's Avatar
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    An AAV needs to be on a system that also has a vent through the roof.
    If this goes out to it's own drain, it wont work.

    If it is connected to a vented system, then it may be that the AAV that isn't working.

    I normally would use a Studor Vent.

    What you have is a $3.00 part.
    The Studor runs about $40.00, but they work.
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    Last edited by Terry; 04-27-2013 at 12:38 PM.

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    DIY Junior Member Jfree's Avatar
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    Thanks for replying Terry, I have tried a real AAC by Oatey retailing for 17.00 and it did the same thing, any ideas?

  6. #6
    DIY Junior Member Jfree's Avatar
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    IT's an Oatey Sure Vent AAV, installed without the rubber band of course
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    Forum Admin, Expert Plumber Terry's Avatar
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    An AAV needs to be on a system that also has a vent through the roof.
    If this goes out to it's own drain, it wont work.

    I forgot to post this the first time, so I went back and did an edit on it.
    If you go to the specs, they "must" be on a vented system.
    If that pipe goes out on it's own, it won't work.

    There's nothing wrong with the Oatey.

    You will need to run a vent through the roof.

    http://www.ipscorp.com/pdf/studor/St...Spec_Sep08.pdf
    Read Installation C.
    A minimum of one vent shall extend to the open atmosphere for every building drainage system.
    Last edited by Terry; 01-26-2010 at 05:28 PM.

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    DIY Junior Member Jfree's Avatar
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    THanks Alot Terry, I just found reference to that. It seems wierd that even the spring loaded trap vent won't allow air in. It takes very little negative pressure to open this diaphram when putting it up to your mouth and sucking, but as I originally posted, the riser seems to have positive pressure when you put your hand over the riser while draining, go figure. I guess I don't really understand what is happening.

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    DIY Member Marty53's Avatar
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    I don't understand, whats the point of an AAV or studor vent if you still need to vent the fixture to the roof?

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    DIY Senior Member Rich B's Avatar
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    I had problems with my kitchen sink draining slowly and backing up into the second side. It was an issue for a long time. I always assumed it was from not having a proper vent and also from crud builtup in the p-trap. It is an old two basin sink. It stopped up completely one day. I worked on it for 2 days. Replumbed it under the sink and added a studor AAV since it had no vent before. It still refused to drain properly and I was advised it was a clogged pipe on another forum. They were old galvanized and that is exactly what was wrong. I snaked the pipes and it took 3 tries with a homeowner model manual snake to get it draining. It was about a 15 foot run to a vertical 4" C.I. stack and that is also the main vent up thru the roof. I eventually replaced all the galvanized with pvc right to the C.I.......drain works perfect, no backups. AAV is still in there as I had no way to add a proper vent. It is a Studor and works perfect with no issues and has been in there for a few years already. Very easy to change if it ever does go bad. I think you have a clogged pipe.....

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    Forum Admin, Expert Plumber Terry's Avatar
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    I don't understand, whats the point of an AAV or studor vent if you still need to vent the fixture to the roof?
    It reduces one vent through the roof.
    Or in some cases allows for an island fixture.

    but when I unscrewed the spring loaded trap vent, lo and behold the water rushes out.
    Does that sound like a plugged pipe? Water rushes out?

    Sounds like a venting issue.




  12. #12
    DIY Junior Member Jfree's Avatar
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    Yes Terry,
    You are right, no clogged pipe, drains mightily, when I open the system to air. Trying to learn a concept here. What I don't understand is the physics of why the trap vent or aav won't suck air in without another vent, why wont the trap vent diapham open to let the air in? It must be that the pressure is greater in the drain system than the atmosphere outside the pipe when the system is closed pushing against the diaphram instead of pulling and when tied into a system that has at least one vent, like in my house, this scenario(aav or trap vent) would work because the pressure inside and outside the pipes would be closer to the same? Am I on the right track here, purely academic at this point. Of course I wouldn't put an AAV on the system if I vented through the roof...

    Of course I wouldn't put an AAV on the system if I vented through the roof...

    But for an AAV to work, it needs some part of the home with a "real" vent. An AAV allows air to suck in, but a real vent allows air to travel "both" ways. So unless you have a "real" vent that allows travel both up and down, then the "cheater" vent won't work. Terry Love
    Last edited by Terry; 01-22-2011 at 11:59 PM.

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