Shared up-the-wall vent for three fixtures?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by littleguns, Jul 17, 2010.

  1. littleguns

    littleguns New Member

    Messages:
    7
    I'm turning a 5x9 porch (over shallow crawl space) into a three-quarter bath with lavatory on east wall, shower across south end, toilet on west wall. I'd like to bring the lavatory drain and shower drain together into a 2" wye, then that wye into the two-inch wye neck of a 3x3x2 fitting that will aim toward my 4" main drainline in the basement. The lav/shower drain would enter the 3" main line a foot or so downstream of the closet bend. All the drains will be horizontal (lying under the subfloor) with proper 1/4" drop per foot until the 3" drops vertically into the 4" basement plumbing. My question is regarding venting. With such short drain lines (nothing more than five feet apart) can I get by with one 2" vent in a wall (either for the lavatory or toilet) serving all three fixtures, or do I need separate vents for each? The vent could go straight up through the roof on either the lav wall or the toilet wall. In other words, do I need three pipes up a wall or will the one 2" vent pipe that joins the drain under the floor be sufficient to vent all three fixtures? I know it is OK to run separate vents for each fixture upward to join one large through-the-roof vent above the ceiling; what I'm asking is whether I can avoid two of those three pipes going up a wall. Is this at all clear what I'm explaining? FWIW, there are no codes or inspections or permits required; I'm in an area where no one officially cares, but I try to do work that would meet typical codes. Thanks for any advice.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,032
    Location:
    Cave Creek, Arizona
    VEnt requirements have NOTHING to do with how close the fixtures are to each other. IT depends on HOW the piping is arranged. From YOUR description, and that is all we have to go by, it is a proper installation, IF you actually install it the way you indicate. Depending on the actual space limitations, however, I might do it completely differently.
  3. nhmaster3015

    nhmaster3015 Master Plumber

    Messages:
    836
    Location:
    The granite state
    Done properly you can wet vent the entire bath group though a single 2" vent
  4. mnzpasquale

    mnzpasquale New Member

    Messages:
    8
    Location:
    New York
    Is this what u are trying to describe ???

    Attached Files:

  5. littleguns

    littleguns New Member

    Messages:
    7
    Yes, that's one possibility. The other would be to have the vent on the west wall, just downstream of the WC bend. Would your illustration work? Thanks for offering it.
  6. mnzpasquale

    mnzpasquale New Member

    Messages:
    8
    Location:
    New York
    I was just trying to get a picture of what u were saying...as for what will work...u need to take advice from Hj , or Wally, they are the pros...I just thought a illustration could help with discussion...
  7. littleguns

    littleguns New Member

    Messages:
    7
    Thanks. I'll be hoping they reply regarding your sketch.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,032
    Location:
    Cave Creek, Arizona
    His should work, always assuming you install it as shown. Your suggestion would not, however. The lavatory vent as shown would HAVE to be installed. Any other vents might be superfluous or redundant.
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