New Drain Install: 4" To Toilet?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by molo, Jul 16, 2012.

  1. molo

    molo Member

    Sep 23, 2006
    Cold New York
    New Drain Lines: Multiple Questions


    A couple questions about new drains on a bathroom renovation. 8' x 8' bathroom

    1. The toilet is about 6' away from the 4" main that drops down and out of the house. Is it a good idea to run 4" over to the toilet, or is nothing gained by doing this because the toilet trap and flange are both 3"?

    2. I have seen sweeping elbows that have a longer bend. Are these required for vertical elbows, or are the standard 90 degree elbows accepted? Directly below the toilet the line turns horizontal 6' and then drops down and out to the main. Can I use a standard 90 elbow below the toilet?

    3. Should the shower and sink each be run directly to the 4" main that drops down and out of the house, or can they be run together and then to the 4" main?

    4. The vent stack is located on the outside wall of the house directly above the 4" main that drops down and elbows out, leaving the house to the main. Therefore all fixtures will be before the vent. Is this OK?

    Last edited: Jul 17, 2012
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    There are advantages of running at least a 4x3 toilet fixture (not sure of the proper name) up to the toilet. This is one instance where you can go from larger to smaller with a drain legally. By running 4" there, as long as the pipe is plumb coming up, you can buy a flange that fits over the pipe and you can then cut off the excess without having to be precise (i.e., there's no hub, it's sort of like a repair coupling and will slide over the pipe). This can make final installation of the flange much easier after the finished flooring is on. Someone more qualified than I needs to address your other questions.
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