Kitchen Sink loop vent in wall above sink flood level w/ connection to main stack below flood level

Discussion in 'Massachusetts Plumbing and Gas Code' started by Richard978, Aug 5, 2021.

  1. Richard978

    Richard978 New Member

    Joined:
    Aug 5, 2021
    Location:
    Boston
    Hi guys,

    I am looking to vent a kitchen sink that doesn't have easy access to the existing vent system. I understand diagram B in the attached image is code for a loop vent as they are typically used in kitchen island where the loop is directly below the counter. In my situation the loop vent would be in a wall and could go above the sink's flood elevation. My question is would the system in diagram A be acceptable as the loop is above the flood elevation at the sink but the actual vent connection to existing main stack is below in the basement?
     

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  2. Terry

    Terry Administrator Staff Member

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    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    [​IMG]

    Your wye coming off the loop is the wrong direction.
     
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  4. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Other than the issue Terry cited, either A or B would be fine for a loop vent. The connection from vent to drain occurs at the low point of the vent; after that point, the vent just has to follow the usual vent rules (other than the height of the horizontal segment), so it can rise up before hitting the main stack.

    But the main question is whether you can get approval for a loop vent for a sink that isn't on an island. Lack of easy access may not be sufficient justification for the loop vent; you may have to just do it the normal, hard way.

    Cheers, Wayne
     
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  5. Richard978

    Richard978 New Member

    Joined:
    Aug 5, 2021
    Location:
    Boston
    Good catch. Yes, the wye would go in the flow direction. Opposite of what I drew. Thank you!
     
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