Proper Loop Vent?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jalloken, Dec 19, 2011.

  1. jalloken

    jalloken New Member

    Messages:
    3
    Location:
    Texas
    I am doing a kitchen remodel where we removed a wall. The wall contained the vent for the kitchen sink. The plumber installed the vent for the sink as shown in the attached picture. I had my brother-in-law over who is also a plumber. He did not like the configuration. Should I be concerned? I have been researching loop vents and do not find any indication that what is installed is a proper loop vent. To me it looks like there will be gurgling while the sink is trying to drain. Like holding a water bottle upside down and pouring it out. Please help!!

    Attached Files:

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,053
    Location:
    New England
    Doesn't look right to me, either. And, it would be difficult to get it run now without moving some copper. Once underneath the floor, which way does the drain line run? Both sides of the loop, I think, need to connect to the drain line separately, not at essentially the same point. One of the pros should comment later.

    [​IMG]
    Last edited by a moderator: Jan 26, 2012
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    It is not proper, and the trap can potentially be siphoned. The diagram which was provided on the other forum shows a proper loop vent, and it would involve some digging now after the fact to implement it.
  4. jalloken

    jalloken New Member

    Messages:
    3
    Location:
    Texas
    I have heard discussion of AAV in this type of situation. Will that work? Pros/Cons?
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,053
    Location:
    New England
    AN inspector will often not allow an AAV when it can be done properly, they are allowed, but not preferred, especially when you are doing this much remodeling and have access to do it right. Gravity is your friend, and a properly installed gravity drain and vent is the most reliable. Plus, you'd have to have an access panel for it since they do wear out and fail...you must be able to get to it to replace it. Assuming you had a permit, it would not pass.
  6. jalloken

    jalloken New Member

    Messages:
    3
    Location:
    Texas
    Is the proper fix to run the loop down to the drain line below slab? Will they have to run a foot vent to connect back into the original vent stack? Thanks.
  7. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    At this point other then a AAV your looking at breaking up the floor. Talk to the inspector.

    John
  8. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    It looks like the wall extends up to the celing at the end of the wall. If this is the case then strap the vent to it and box it in. tie in the vent in the ceiling. If the wall extends up to the ceiling at any point then it is not an island. The inconvienence of having to box it in is not a valid excuse to island vent and most (but not all) inspectors won't allow it. Given the choice of leaving it as it is I would use an AAV.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    The "loop" appears to be too LOW for a proper loop vent. The only salvation for your installation, since it has many things wrong about it, is that by the time siphonage would occur, the flow in the pipes should be small enough that air and water can both flow in the pipe, thus giving a modicum of venting action to prevent the trap siphonage.
  10. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    You know, I'm looking at that and thinking it's like a monkey fing a football but then....the loop is all 2" with a 1 1/2" trap arm dumping into a san-tee which is good and since it is all 2" it may just work ok because there is enough air movement in the loop to prevent trap siphonage. I think I'm gonna mock that up in the lab and see if I can get the the trap to siphon. Maybe even hook the manometer up at the top of the loop as see what I get for vac or pressure. I have a gut feeling that though it in no way meets code and is a pretty funky way of doing things, it may just work.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    While the sink is draining, there is no need for a vent, and by the time he DOES need a vent, the flow will be dimished to the point where air can travel through the "loop" to prevent siphonage, but it is still too low and installed incorrectly.
  12. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    Yep it is indeed, no argument there but short of wacking it out and going with an AAV I don't see a lot of options there if there either. I suspect that if it were in my own house I would close my eyes or look the other way and hook it back up again. After all, it was working when he exposed it.
  13. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    quote; it was working when he exposed it.

    Isn't that the eternal lament of the DIYer? "It is working, so why do I have to change it just because some code says it is wrong?" I will say, however, even though we do NOT have dimensions for that drain line, I THINK he may be asking "how to I connect my sink when the drain in the wall is too high?", by the time he finishes.
    Last edited: Dec 22, 2011
  14. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    Could be, yes. If it's got a basement under it then it is a pretty easy fix. If it's slab that complicates the issue considerably though.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    It is a slab, but it only complicates things slightly, because concrete breaks pretty easily.
  16. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    agreed, now let's see how far he's willing to go to make it right.
  17. mtcummins

    mtcummins In the Trades

    Messages:
    380
    Location:
    Pittsburgh PA
    Why not do both? If one hack method that might work is there, why not add a 2nd not great method... bring a tee off the right side of the loop into the cabinet, up a few inches (to get above trap 4" plus), and pop an AAV on that bad boy. Redundancy in hack work is good, right? If the loop fails, the AAV is there, if the AAV fails, the loop may work...

    In case anyone missed it, I'm not being serious.

    If there's any way to take that vent through the wall and up around to tie back into the original vent, I think that would be preferable. I think it would still be illegal though, to have the vent run horizontal at lower than 42", but it would still be better than what you have, I would think. If you do that, I'd put in 2 cleanouts... one on the sink drain near the floor, and another on the horizontal vent line, just in case you have a backup that gets into the vent horizontal, will allow you to clean it out.

    If there isn't a good route, this looks like a good AAV candidate to me though. It seems like you have a reasonable reason to do so. If you do that, cut out all that crap, bring a trap arm over to a santee above the drain through floor, go up a few inches, and stub out over there to put an AAV inside the cabinet, not in the wall. Make sure the AAV is at least 4" above the trap. And as mentioned, check the height of that drain, I think the standard height for a kitchen sink rough in is 18" off the floor, that looks too high.
  18. mae-ling

    mae-ling New Member

    Messages:
    14
    Location:
    Vancouver, BC
    That looks like what a plumber told me to do for my island dishwasher. Called it a "Barbers Loop" said he preferred it to a "Island Loop". I could not find anything on it and decided to do the Island Loop.
  19. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    He could call it anything he wanted to, (even a "yoke vent" because it looks like the yoke they hold cows with while milking them, and we called the "island vent" a "yoke" for the same reason), and he preferred it because it was easier and cheaper.
  20. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,184
    Location:
    Maine
    Barber's loop is a new one to me.
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