Vent for Kitchen Sink with Large Window

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Stu27, Apr 10, 2013.

  1. Stu27

    Stu27 New Member

    Messages:
    22
    Location:
    Northern Virginia
    Part of our kitchen remodel involves the addition of a large window (12 ft) with a centered kitchen sink. How might one vent the sink in this configuration? I could put an AAV in there, but because I have an existing roof vent for the kitchen sink, I'm thinking why not try and use it?

    Attached are several drawings that show a vent idea that picks up the existing roof vent.
    as drawn:
    1-1/2 inch trap
    2 inch drain
    horizontal drain length is about 23 feet to existing vertical waste stack
    horizontal vent run is about 6-1/2 feet
    vent penetration through roof is at existing location

    Do you think I'd have a chance at getting an exception for the horizontal run that's below the flood level rim of the kitchen sink? Would the cleanout in the attic and the two long sweeps downstream to the horizontal vent run help with that exception? I've kinda got tunnel vision, stuck on only this and the AAV idea… what other options are there?

    Thanks,
    Stu

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  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,258
    Location:
    Cave Creek, Arizona
    The length below the sink connection is immaterial. A cleanout in the attic would be useless. You DO need a cleanout below the sink connection's "T", and that could be used to clear any obstruction in the overhead vent. It is up to the authorities whether that offset would be acceptable, but there is no reason it should not be in this case. I have even used an "island vent" setup with the foot vent connected back to the vent through the roof.
  3. Stu27

    Stu27 New Member

    Messages:
    22
    Location:
    Northern Virginia
    Thanks hj. I'll see what the inspector says about this updated setup.

    I was struggling with the island vent option… keeping both the foot vent and the drain with the joist bay. It seems while the foot vent could sit in the joist bay in the basement on it's way to the nearest wall, the drain would end up below the joists and probably end up stuck at the beam on it's way to the stack, unless I really lowered the drain to an uncomfortable level below the beam.

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  4. asktom

    asktom Member

    Messages:
    589
    Location:
    Victor, MT
    Is there a vent for the toilet that you don't show? Using the kitchen drain as a horizonal wet vent isn't going to cut it.
  5. Stu27

    Stu27 New Member

    Messages:
    22
    Location:
    Northern Virginia
    I didn't draw those details. The toilet is wet vented off the lav sink (original build).
  6. Stu27

    Stu27 New Member

    Messages:
    22
    Location:
    Northern Virginia
    Here's the detail of the as-built (1984) toilet vent. The lavatory drain is 1-1/2 inch to the wye. Virginia uses the 2009 IPC. Is this vent arrangement code compliant?

    Attached Files:

  7. speede541

    speede541 Member

    Messages:
    124
    Location:
    San Francisco Bay area
    On that note, I've got a somewhat similar situation, but with the drain offset from the sink. Since the 'T' point will be behind a dishwasher, the inspector has suggested I add my cleanout to the horizontal arm, for easier access from under the sink cabinet (rather than having to pull out the dishwasher). I'm considering either location marked '1' or '2' as opposed to the standard location '3'.

    However, as HJ noted, I've been under the impression that location '3' is used to clear blockages in either direction. A cleanout on the arm would only allow my snake to make the turn to clear the drain, not the vent.

    So even if the inspector is approving '1' or '2', should I install a location '3' too, in keeping with best practice?

    (FYI, the entire horizontal section is running out-of-wall.)

    [​IMG]
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,258
    Location:
    Cave Creek, Arizona
    There is a window in the wall so that must be an exterior wall. In this area we would install the cleanout at position #3, but rotate it 180 degrees so it faced to the outside.
  9. speede541

    speede541 Member

    Messages:
    124
    Location:
    San Francisco Bay area
    Hmmm... I'm hesitant to punch through my stucco for that since the inspector isn't asking for it, though it sounds like the cleanest solution. I think I'll err on the side of caution and install two cleanouts.

    Thanks, HJ!
  10. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,312
    Location:
    Maine
    If the horizontal portion of the vent is 6" above the flood level rim of the sink, then it's ok. Otherwise, not.
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