Kitchen sink venting height

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jaydub2010, Mar 31, 2013.

  1. jaydub2010

    jaydub2010 New Member

    Oct 1, 2010
    Whidbey Island, WA
    So my situation is this..opening up a half wall on back side of kitchen sink. Want to lower the overall height of the existing half wall, which means we will need to lower the sink vent as well. The vent takes a 90 degree turn at roughly coutertop height. My question; is there a specific height requirement before the vent can take that turn? that is, does it need to be a specific height above the P-trap? any feedback would be appreciated
  2. asktom

    asktom Member

    Nov 9, 2009
    Victor, MT
    The vent needs to be 6" above the top of the countertop when it makes the 90 and the slope towards the sky at at least 1/4" per foot after that. You might be able to move the drain to the side, if it isn't too far (42" for 1 1/2"). Another other option is the type of set-up used for island sinks, you can find out about them by searching this site.
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  4. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    In Washington State they may allow a lower turn if you can't go higher.
    You would use waste fitting below flood level, not vent fittings. We sometimes do this if we are below a window.
    Normally it's six inches above flood lever, (42") which is likely what yours is now.

  5. jaydub2010

    jaydub2010 New Member

    Oct 1, 2010
    Whidbey Island, WA
    The existing vent does run about that 6" above the top of the counter top. And if I understand you correctly (and I apologize in advance if I don't), but since my lowering of the horizontal run would be below the top of the sinks or "flood level" I can get away with lowering it as long as I use "waste " fittings instead of "vent" fittings?
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    If you can't go high enough, then you may need what is called a loop or island venting system. Search on that to see what's involved.
  7. lothia

    lothia New Member

    Apr 30, 2013
    Seattle, WA
    I hate to push up an old topic, however jaydub2010 had the exact same question that I did. I live in Seattle in a midrise (7 floors) for some reference.
    What Terry posted is the standard way to vent if you have a two tier peninsula or if the sink is against a wall, however what jaydub2010 wanted/wants to do is change the two tier peninsula to a single tire which means that it is impossible to get 6" above the floor line until you are at the next wall.

    My question is the same, I am removing a pony wall which removes my horizontal vent that is 6" above the floor line are there any possible ways to vent this with a modified loop vent differently for a peninsula then a island? The reason I ask is that the peninsula shouldn't require the foot vent to be under the floor as it could be behind the cabinets just below the floor line and then do the traditional loop correct?
    Are there any other ways to vent a peninsula then a studor or loop if you are within 4 feet of the stack and you aren't required to put all the plumbing below the floor?

    Perhaps I am looking at this all wrong, would a dirty arm work even though you are not at the 42" spot?

    jaydub2010 if you are reading this, what was the solution you came up with in the end?
    Last edited: Apr 30, 2013
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