Why is loop venting generally prohibited?

Discussion in 'IPC Plumbing Code Questions' started by Sproutnik, Jul 18, 2018.

  1. Sproutnik

    Sproutnik New Member

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    Jul 17, 2018
    Location:
    North Carolina
    After running into the problem of how to vent my yurt without roof or side-wall penetrations, I realized that a loop vent would appear to solve all of my problems by allowing me to run a vent under the floor and up the exterior side of my yurt wall. However, loop venting under the IPC is limited in use to sinks. This got me curious!

    Anyone know the history/rationale behind the usage of loop venting becoming so limited in scope?
     
  2. Terry

    Terry Administrator Staff Member

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    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    For kitchens on an island where a vent can't go straight up, they came up with the island loop venting, which still incorporates a vent through the roof, but in a location further away. That vent has a cleanout to make sure it can be cleared of sludge.

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    Last edited: Nov 13, 2018
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  4. hj

    hj Moderator & Master Plumber Staff Member

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    You CAN"T install a loop vent entirely under the floor, because the "loop" feature STILL has to be as high ABOVE the floor as possible, usually at least to the bottom of a 36" counter top.
     
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  5. Sproutnik

    Sproutnik New Member

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    Jul 17, 2018
    Location:
    North Carolina
    I understand this. For me, the desired feature of the loop vent is that it connects to the "foot vent" that runs under the joists to a vertical vent, which could run up along the outside of the exterior wall, since on my yurt I cannot penetrate the wall or the roof.

    However, my question was driven by curiosity, and still stands unanswered -- why are these only allowed on islands? Reading code from the 1960's, it appears that they used to permitted in far more applications where there was no direct access to the vertical vent except running horizontally under the floor.
     
  6. Sylvan

    Sylvan Still learning

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    plumbing- - fire suppression
    Location:
    New York
    Notice they require a CO under the trap. DUHHHHHHHHH

    Suppose there is a stoppage just beyond the combination fitting wye 1/8 ben and grease flows up up the vent pipe above the LTTY then how is is supposed to be cleaned?

    This would of course would render the vent totally useless

    I would think the vent line should require a CO as the trap is already allowing access to the waste line
     
  7. Sylvan

    Sylvan Still learning

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    Occupation:
    plumbing- - fire suppression
    Location:
    New York
    Vent "threw " roof I think through will be better
     
  8. hj

    hj Moderator & Master Plumber Staff Member

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    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    I have used the "loop vent", ( we called it a "yoke vent", like the ones they use for cows when milking), when the sink is under a window that is between two beams with no possibility of drilling through them.
     
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