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Thread: is this drain adequately vented?

  1. #1
    DIY Member adrianmariano's Avatar
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    Default is this drain adequately vented?

    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 by adrianmariano; 01-30-2007 at 05:48 AM.

  2. #2
    Homeowner geniescience's Avatar
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    Quote Originally Posted by adrianmariano
    ... a 90 degree elbow and about 18 inches of vertical pipe, then a gradual bend ...
    Vertical Drop? no good.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default vent

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

  4. #4
    DIY Member adrianmariano's Avatar
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    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. #5
    Plumber/Gasfitter dubldare's Avatar
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    Quote Originally Posted by adrianmariano
    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.

    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 .

    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.
    --Customers of plumbers: Never be afraid to ask for proof of licensure of the plumber servicing your equipment. A licensed plumber will be proud to show you his personal license.--

  6. #6
    DIY Member adrianmariano's Avatar
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    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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