Air Admittance Valve on 3"

Discussion in 'Remodel Forum & Blog' started by Robby, Dec 20, 2012.

  1. Robby

    Robby New Member

    Dec 20, 2012
    We are looking at adding a toilet and sink in a small closet. The area is on a crawl space and there is an unused closet behind it where I can connect the sink vent and install a 5' tall 3" stack with a 3" air admittance valve. We are also looking at adding a washer upstairs. We thought we might use a 2" air admittance valve there too. Will this setup work well? See photo. Any suggestions would be greatly appreciated. How how would the air admittance valves need to be in relation to sink or washer drain?


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  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    The lav can wet vent the toilet, using a 3x2 wye or combo fitting, running the lav in 2", and then terminate with a 2" AAV with access.
    No need for a 3" vent stack.

    The washer upstairs on the separate 2" going upstairs can only have an AAV if there is at least one open air vent going through the roof. Though I would check on that, because there might be positive pressure on the washer vent when it pumps out. It's best go go atmospheric there.
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