do AAVs expel sewer gases?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by pronouncedeyen, Nov 12, 2013.

  1. pronouncedeyen

    pronouncedeyen New Member

    Messages:
    46
    Location:
    Baltimore, MD
    This may be a stupid question but if an AAV remains closed until it receives negative pressure from water going down the drain then how does it expel sewer gases? What happens to them if you use an AAV?
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,423
    Location:
    IL
    A properly-operating AAV only admits air. Sewer gases will make it out of the sewer after or during the sewage passage. Eventually it will go by a vent.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,129
    Location:
    Bothell, Washington
    An AAV needs a proper vent somewhere in system for postive pressure. There should be at least one vent through the roof for that.


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    Last edited: Nov 12, 2013
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,143
    Location:
    New England
    Only when they fail...
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    I question item E, because there is no way to "engineer design" the installation to vent trapped air in an ejector pit if there is no "atmospheric vent" and/or the water in the pit rises above the inlet piping.
  6. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,227
    Location:
    Maine
    Well now HJ, if you log on to the Studor web site you can find an engineered drawing for just such a thing. Of course, as you look at it you will note that the way they have the AAV installed it pretty much does nothing. LOL
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,129
    Location:
    Bothell, Washington
    I think most of the plumbers would refuse to use them on a pumped system.
    I remember on one basement installation where I went to the next floor and used the 2" toilet vent.
  8. asktom

    asktom Member

    Messages:
    575
    Location:
    Victor, MT
    AAVs are lazy plumbing. They will eventually fail, no matter how the Studor folks frame it. AAVs are from the "wham bam thank you mam" school. Gravity, which includes atmospheric pressure, will continue to work indefinitly. Vent it right and it is a done deal.
  9. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,227
    Location:
    Maine
    Honestly, other than an island sink and even there I'd rather waste stack vent, I have never in near 40 years of plumbing installed one and never will. I have always been able to find a way to properly vent the fixture and if the homeowner doesn't want the expense or possibility of having to do sheet rock repairs, I walk away from the job. Not interested in hack work and better than that, I don't need it either. Then again I feel the same way about PEX, flexible supply tubes and plastic J hook hangers. We don't stock any of the above, don't use any of the above and I would probably fire any plumber working for me that did. Add CSST for gas piping to the list LOL
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