(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 6 of 6

Thread: Basement plumbing AAV question

  1. #1

    Default Basement plumbing AAV question

    When we had our 2-year old house built, we had the basement roughed-in for a full bath and bar sink.
    The bath rough-in seems to have the tub and WC drains wet vented to the lavatory drain which is capped off with an AAV.
    The bar sink drain is also capped off with an AAV.

    It's time to finish the basement and my question is, is it ok leaving the AAV's for the vents, or do they need to be tied in to the rest of the house vent system?
    Both AAV's will be in undersink cabinets, so will be accessible. Local code allows the use of AAV's as long as there is at least one normal vent to the outside.
    The rest of the house is vented normally with multiple roof vents.

    I'm willing to accept the risk that if one of the valves malfunctions that there would be sewer gas smell until it was repaired. Would there be an explosion risk as well?

    Thanks in advance for any advice...

  2. #2
    In the Trades kordts's Avatar
    Join Date
    Oct 2005
    exurban Chicago


    One vent down there has to be tied into the rest of the vent system. Don't worry about explosions.

  3. #3
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    There could be an explosion.....but you would have to eat a whole lot of beans.....methane gas.

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default vent

    Without at least one vent tied to an atmospheric vent, the system will become a closed system, which will prevent all the basement fixtures from draining properly, or even draining at all.

  5. #5


    Is it enough that the rest of the house is vented atmospherically and these drains meet up with the main stacks?

    The bath and bar sink are on opposite sides of the basement.
    So basically, there's one sink drain on its own branch that has an AAV and then ties into the rest of the drain system under the basement floor.
    And there's the bath branch that has the tub, toilet, and lav vented at the lav with an AAV. It also ties into the rest of the drains under the basement floor.

  6. #6


    I talked to my local board of health plumbing inspection department and they said that the AAV's are perfectly fine as they were installed during the rough-in. I do not need to add any additional venting.

    I will be applying for a plumbing permit as well as a building dept permit for the basement addition. They said that since the drains were roughed-in when the house was built that the first plumbing inspection would be after framing is complete and the water supply lines are put in. Then there will be a final inspection after the finish work is done and the fixtures are installed.

    Thanks for everyone's advice and help! This forum is an awesome resource...


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts