Base Cabinet drain re-route

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by dgold, May 19, 2013.

  1. dgold

    dgold Product R&D for a powertool manufacturer

    Messages:
    82
    Location:
    Carlsbad, CA
    Scenario
    In a kitchen remodel, and discovered a complication. The builder ran a 1-1/2" drain pipe behind the base base cabinets along the wall. Unfortunately, where the horizontal drain line is, to the left of the sink, the wife wants pull-out trash bins. Said bins will interfere with the drain line. The wall itself is a 2x4 exterior wall, so routing the plumbing inside the wall - through studs - isn't feasible.

    Routing Question
    I'd like to route the drain pipe down, then along the floor (so below the base cabinets - and hidden by toe kick), and back up again through the bottom of the sink base cabinet. I tried my best to indicate with the red lines how I'd like to do this. Essentially it creates a double trap. Is this a legitimate method to accomplish what I'm trying to do?

    Pipe Selection Question
    The pipe shown in the picture, as well as the vertical (in the wall) are 1-1/2" ABS. As I turn down from the wall, should I open it up to 2" pipe to help the water drain better due to less drag? Or does the 1-1/2" bottleneck at the vertical negate that logic?

    Plumbing 2.jpg

    Thanks for reading
    David
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,349
    Location:
    Yakima WA
    I don't see a vent. Without a vent before the drain turns downward after the P trap, you have an illegal S trap.
  3. dgold

    dgold Product R&D for a powertool manufacturer

    Messages:
    82
    Location:
    Carlsbad, CA
    Can is use a tee and a ready-vent?

    Any value in upsizing the new drain line, or should I just do the whole thing in 1-1/2" to keep things simple?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    You absolutely CANNOT do what you show. It would violate EVERY code and good plumbing practice, besides creating a nightmare for you when you use the sink. Why can't you run the line inside the wall. With the window above it, the studs are NOT "structural" and we ran drain lines inside 2x4 walls for "decades" before 2x6 walls became common. You also cannot "upsize" a drain line and then "downsize" it again. Also a major violation.
  5. dgold

    dgold Product R&D for a powertool manufacturer

    Messages:
    82
    Location:
    Carlsbad, CA
    Thanks HJ. Appreciate the feedback - especially so quick and before I got started down that path.

    Unfortunately I have a gas line running vertically in the wall along the way to the sink, so I won't be able to run this in the wall. I'll run it inside the base cabinet and just figure out something for the trash bin.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    Why is there a gas line there? It appears to be a "short wall" under the window so it cannot be going too far upwards.
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,004
    Location:
    Bothell, Washington
    The plumbing takes presidence over trash bins.
    That's why you have a plumbing inspector, and plumbing permits.

    [​IMG]
    Last edited: May 20, 2013
  8. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    you can do it your way sort of just don't go up,
    go down and tie in under the floor !

    and yes you still need to run vent up though roof CA plumbing goes by the UPC.
    and requires vent though roof !
    where the black abs meets the white painted abs throw a Wye in the line run it up under window then back over to tie into existing vent,
    make the existing drain tie in a clean out and cut back into pipe under the floor that is the way a plumber might run it and meets code, and practice,
    and your wife can have her trash bins

    Remember with drains it is always down and never ever up
    Last edited: May 20, 2013
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