Kitchen peninsula venting

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by bsperr, Feb 22, 2010.

  1. bsperr

    bsperr Member

    Messages:
    74
    Location:
    Athens, GA
    Sorry for the lousy drawing, but I'm trying to figure out the best way to vent a sink for a kitchen remodel. I'll be building a peninsula counter top between my kitchen and den that will consist of a 2' partition and a 5' 8" pony wall with a 42" high bar top. The first pic is a simplified graphic of the framing and dwv. If I tuck the vent pipe right under the bar top, it should be close to 6" above the flood rim of the sink (under mount) before turning horizontal. The second pic is an exported view of the kitchen from sketchup to give more reference.

    Does this venting look correct? Would I need the relief vent depicted in light blue? Thanks for your help

    Attached Files:

  2. jc60618

    jc60618 DIY Junior Member

    Messages:
    88
    Location:
    Chicago
    The picture I included would pass inspection in my area. In Chicago your p-trap can be 5 feet from the vent.

    Attached Files:

  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,689
    Location:
    Cave Creek, Arizona
    You could do it that way, or you could angle it up at a 60 degree angle, or arm it over like the other drawing,using a 2" pipe. 1 1/2" pipe would not work in that case.
  4. bsperr

    bsperr Member

    Messages:
    74
    Location:
    Athens, GA
    Thanks JC and HJ. I hadn't though about just extending the trap arm, but that would definitely be easier. We're under the 2006 IPC down here in Georgia, so it looks like I can go up to 6' to the vent with a 1 1/2 pipe. Would there be any disadvantages to the longer trap arm? I was thinking about using the arm over so that I could put a clean out above the trap and in the crawl space on the end of that horizontal branch. I was planning to use 2" pipe, but, out of curiosity, why wouldn't 1 1/2" pipe work with the arm over?
  5. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    11/2 trap can only go 31/2 feet because after that the backpressure will slow the draining draining process..
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,689
    Location:
    Cave Creek, Arizona
    IT is a theoretical limitation. At 1/4" per foot slope, once a 1 1/2" pipe goes more than 6 feet, it reaches the point where it technically could create an version of an "S" trap and cause siphonage. It has nothing to do with back pressure.
  7. Paulypfunk

    Paulypfunk In the Trades

    Messages:
    11
    Location:
    Seattle
    In looking at your original photo, yes you could pull a vent into the peninslula as long as you use drainage style fittings and drainage slope for your pipes, until it reaches the point that is 6" above flood rim (countertop) with no connections to other vents below that flood rim. I don't see why you would need the relief vent.

    That being said, I also would enlarge the trap arm to 2" to give yourself the 5' (the max UPC distance, I guess 6' in your juri.) distance from the vent. Much simpler.
  8. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    If he runs 2", he can go up to 8' under IPC (or 6' with 1.5"). The trick, though, is to keep the slope right at 1/4" per foot for these max distances. If you go more, the drop will be too much and will effectively create an s-trap.

    Since he would not be near the limits for either size under IPC, the 1.5" would be just fine. He just has to make sure that the slope is at least 1/4" per foot, but less than 1/2" per foot (to prevent s-trap over 3' distance).
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