is this drain adequately vented?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by adrianmariano, Jan 30, 2007.

  1. adrianmariano

    adrianmariano New Member

    Messages:
    79
    Location:
    Massachusetts
    I have a kitchen drain as follows:

    P-trap followed by 12 inches horizontal pipe, then a 90 degree elbow and about 18 inches of vertical pipe, then a gradual bend (two 22.5's I think and another foot of pipe) and the pipe finally connects to the vented drain pipe. The connection to the vented drain pipe is about 3-4 feet below the P-trap.

    Is this OK or am I at risk of siphoning out the trap?
    Last edited: Jan 30, 2007
  2. Vertical Drop? no good.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,045
    Location:
    Cave Creek, Arizona
    vent

    Unless the vent connects to a tee instead of that first elbow, you do not have a vent.
  4. adrianmariano

    adrianmariano New Member

    Messages:
    79
    Location:
    Massachusetts
    I guess this explains the occasional bad odor. (It's really been a pretty rare thing.)

    Is there any reason not to rectify this problem with an air admittance valve? The alternatives appear to be impractical given that the existing vent pipe is buried in the wall behind cabinets.
  5. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND

    It wasn't impractical when that piping was installed, it was just too much work or lack of knowledge, or a combination of the three :D .

    Are you sure that that stack does not serve any fixtures above?

    As far as the AAV working or not, not going to go there. They are not legal here, and IMO, only serve as a way to cut corners.
  6. adrianmariano

    adrianmariano New Member

    Messages:
    79
    Location:
    Massachusetts
    I can't imagine why the piping was done the way it is done. The house was built in 1954. The vent serves only the utility sink (in the basement) and the kitchen sink. (There is nothing above.) The connection for the kitchen is in the basement well below the trap, but the pipe runs up right through the kitchen wall so there's no reason a horizontal connection couldn't have been made. The kitchen was remodeled in 1996, I believe, by the previous owner and that would have been an opportunity to fix it when they replaced all the cabinets. I don't even think it would have been that much more work, so I think it must have been lack of knowledge, rather than laziness, that is at fault.

    At either time (original construction, or remodeling) it would have been a simple matter to do the job correctly. But now, for me to fix it does not appear so simple. If I want to avoid an AAV I'd have to make a loop which I think is possible (but I'm not sure as I don't understand exactly what the requirements are for the loop). It can be fixed properly (and easily) the next time the kitchen is remodeled....
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