DWV Layout Question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by philwgreen, Jul 25, 2013.

  1. philwgreen

    philwgreen New Member

    Messages:
    26
    Location:
    Dallas, TX
    In the process of building a garage addition that has living space above. There is a single bathroom on the second story with a lav, toilet and shower. The bathoom is 12' long with the toilet and shower on opposite ends. The main stack will pass up through the wall next to the shower.

    Just getting ready to start my rough in and wanted to run my dmv diagram past everyone here. My main questions are:

    1. First off, does this diagram look correct or am I way off?
    2. There is a utility sink on the first floor, I know I can't vent it using the bathroom lav drain but can it connect to the lav vent in the attic? And can that vent tie back into the main stack or does it need its own roof penetration? In my drawing I have it going up through the roof.
    3. My toilet is roughly 12' from the main stack so I've added a vent. Would a 2" vent be sufficient for the toilet?

    Any help/feedback is appreciated.


    bathroom_dwv.jpg
    Last edited: Jul 25, 2013
  2. philwgreen

    philwgreen New Member

    Messages:
    26
    Location:
    Dallas, TX
    Looked back at my drawing this evening and realized I don't think I can vent the toilet coming off the horizontal. Reworked the drawing a bit and also tied the first floor lav vent in above the second story sink.

    We're under IPC here and from what I've read there doesn't seem to be a distance limitation for the toilet vent...I may be wrong about that though. However, if I did want to vent properly - would my revised drawing be the way to do it? I didn't know if there was any danger is the toilet siphoning any of the other traps.

    Thanks again for any help in advance. bathroom_dwv_v2.jpg
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,058
    Location:
    Cave Creek, Arizona
    Your toilet vent is still horizontal. As long as any trap is PROPERLY vented it will not siphon.
  4. philwgreen

    philwgreen New Member

    Messages:
    26
    Location:
    Dallas, TX
    Thanks hj.

    So if my other vents are correct (i.e. my drawing) , am I ok not venting the toilet?

    If I were going to vent the toilet how do I do it so it's not horizontal?
  5. Chris B.

    Chris B. Electrician

    Messages:
    19
    Location:
    Toronto, Ontario
    Use the lavatory drain as a wet vent.
  6. Chris B.

    Chris B. Electrician

    Messages:
    19
    Location:
    Toronto, Ontario
    You can tie the vents together once you are (some distance governed by whatever code you are under, say 6") above the flood level rim of the upstairs lav.

    Maybe the stack should be on the toilet side of the room.
  7. Chris B.

    Chris B. Electrician

    Messages:
    19
    Location:
    Toronto, Ontario
    Or have two, and tie them together under the garage floor.

    (This forum won't let me save edits to my posts).
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