AAV Layout for Basement 3/4 Bath- Please Review

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by nwbearcats98, Dec 14, 2005.

  1. nwbearcats98

    nwbearcats98 New Member

    Messages:
    7
    I am finishing my basement with a 3/4 bath. It is not close to the venting stack(s), so it looks like I need to use an AAV. The shower stub is a 12" x 12" square in the concrete floor with a horizontal 2" pvc pipe capped, under the concrete it converts to the main drain and drains past the WC, which is vertical through the floor, the main drain then goes down to the lav drain (2" pvc) that is vertical through the concrete. Does this diagram show the best (only way) to use an AAV to vent this system?

    Thanks in advance!

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  2. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    The shower then water closet order is troublesome; you run the risk of syphoning your shower trap dry. Pretty sure 2004 IPC allows that order of fixtures but prior to 2004 it was considered a no-no and most consider it bad practice. Can you connect the lav to your waste line in between the shower and water closet then loop to your location (or branch arm in wall to pick up the lav)?
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,833
    Location:
    Cave Creek, Arizona
    aav

    If you are determined to use AAV's, or even if not, you have to have one, or some sort of vent, beteen the shower and toilet connection. Otherwise the toilet's water flow will create a low pressure area and suck the water out of the shower's trap.
  4. nwbearcats98

    nwbearcats98 New Member

    Messages:
    7
    These drains are under concrete and this is the standard rough-in setup by local plumbers. So, are they just stubbing basements to get that extra profit without regards to how the finishing aspect is suppose to work?

    Also, will it really create the low pressure area, being that the drain line is horizontal with a slight slope, therefore the drain will probably never create an internal seal with the drained water?
  5. nwbearcats98

    nwbearcats98 New Member

    Messages:
    7
    With the above diagram, I can chip away some concrete by the opening in the floor for the shower drain, connect a 2" wye on the drain, run a 2" vent angled up and over until I am to the studded wall. From there I can run it vertical and use an AAV or run it up to joists then horizontal out the house to exit under wrap around porch. This will put the vent in between the shower and WC. Will this satisfy the venting for all fixtures?
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,833
    Location:
    Cave Creek, Arizona
    toilet

    The water from the toilet as it moves from the toilet down the pipe is going to create a "vacuum" behind it and that will draw the water from the shower trap. I do not know what kind of plumbers you have in that area, but a good one would never install the piping that way.
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,130
    Location:
    Bothell, Washington
    Nor would any inspector let you do it either.

    The proper fittings for all the vents is the right way to go.
    Pipe and fittings don't cost very much.

    Having a home that smells like a sewer just isn't nice.
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