Plumbing pedestal sink under floor

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by llt01, Mar 20, 2006.

  1. llt01

    llt01 New Member

    Messages:
    3
    I am ready to install a pedestal sink in my dpwnstairs bathroom. It seems to be easier if I were to plumb the main drain down through the floor and then install the p-trap and additional piping to the main line (unlimited access). Is this legal or should I try to pipe the p-trap above the floor?
    Last edited: Mar 20, 2006
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    What you are proposing is an S-trap, which is disallowed by all plumbing codes I Know of.
  3. llt01

    llt01 New Member

    Messages:
    3
    Please correct me if i'm wrong. Doesn't a P-trap come down vertical from the drain then form a 180 deg loop up then elbow 90 deg to a horizontal run? This is what I would like to do, if I can. Is there a specific measurement the P-trap needs to be from the sink's drain?
    Last edited: Mar 20, 2006
  4. plumber1

    plumber1 Plumber

    Messages:
    1,423
    Location:
    Florida
    No it would then go through the floor and be re-plumbed to a different place.
    Yes it goes horizontal then.......
  5. prashster

    prashster New Member

    Messages:
    941
    I don't think you should do what you're proposing. I understand from your original post that you want to install a standard p trap - you just want that trap to be below the floor, instead of a few inches under the sink.
    Codes dictate that the trap be located no greater than a certain distance (I think it's 24").

    I haven't found a technical reason for this, but I *believe* it has to do with the fact that water falling from a greater height might push the water out of the trap.
  6. llt01

    llt01 New Member

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    3
    Please See Attached File

    Attached Files:

  7. casman

    casman New Member

    Messages:
    78
    Location:
    New York
    I believe prashter is correct there is a max length to the vertical drop and I think its to prevent water due to its drop from being pulled out of the trap.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    trap

    you cannot do it with the trap under the floor. Even if you could you would still need a vent. Installing the "P" trap above the floor, the way you describe would create an "S" trap out of the "P" trap. You could create a serious drainage, and odor, problem if the pipe from the drain to the trap were that long.
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