Island Loop Vent - Correct Installation?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by dekay, Nov 11, 2012.

  1. dekay

    dekay New Member

    Messages:
    3
    Location:
    Oakland, CA
    Hi,

    Island Loop Vent.jpg As part of a kitchen remodel, we are moving our island sink. The loop vent needs to be modified, but it looks like the current installation is not done correctly, and we may have an inspection issue if we keep it. The pipe to the exterior vent is connected to the drain side of the loop instead of the vent side, and the clean out is also on the drain side. I have created a simple diagram showing what I mean.

    What do you think - Will a loop vent work correctly in this configuration? Would it pass a typical inspection?

    Thanks!
  2. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,314
    Location:
    Maine
    Needs a clean out on the horizontal vent run and another at the base of the stack.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,423
    Location:
    Bothell, Washington
    Something like this
    A cleanout can be in the sink cabinet, that's still considered end of line.

    Waste line 2"
    Vents and trap arm, 1-1/2"
    [​IMG]
  4. dekay

    dekay New Member

    Messages:
    3
    Location:
    Oakland, CA
    Terry, TomSawyer:

    Thanks for the advice. Specifically, looking at the diagram Terry posted, if the vent line is connected just below the in-cabinet clean-out, under the floor, rather than on the other side of the loop, will the the sink drain properly?

    Dekay
  5. Terry

    Terry Administrator Staff Member

    Messages:
    15,423
    Location:
    Bothell, Washington
    The "foot vent" goes on the "vent" side.
    Your drawing is backwards.
  6. dekay

    dekay New Member

    Messages:
    3
    Location:
    Oakland, CA
    My drawing, unfortunately, is how the current sink is vented, with the foot vent connected to the "drain" side rather than the "vent" side. I haven't had any issues with slow drainage, but it sounds like I may need to replumb the venting on the loop per the picture you posted.

    The way the sink is currently vented, it's almost as if the loop wasn't there.
    Last edited: Nov 11, 2012
  7. wjcandee

    wjcandee Wise One

    Messages:
    1,983
    Location:
    New York, NY
    I think the key phrase for you on Bert's diagram is "loop returns to drain line downstream of fixture drain". So you want the trap arm from the p-trap to run to the upstream side of the loop, which is also where I think you want the clean-out; everything can remain in the same configuration but for side of the loop to which the p-trap is connected. There's a maximum length to that trap arm, but it's 3-feet-6-inches on a 1-1/2" pipe, so that should be well-within-range of the other side of the loop. Bert doesn't seem to make a big deal out of trap arm length (judging, at least, from one photo of a washer standpipe installation in his tips [the middle one, which looks like it has a 2-3 inch trap arm]. Tom Sawyer, however, does. But I don't think you'll have a problem making it work.
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