Double fixture fitting for toilets

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Wally Pfautz, Jul 5, 2006.

  1. Wally Pfautz

    Wally Pfautz New Member

    May 19, 2005
    Is there a minimum length requirement (UPC) between a double fixture fitting and closet flanges used for back to back toilets. Another thread alluded to this. I need to use a 10" rough-in toilet on one side, which puts the length from centerline of toilet flange to centerline of DFF vent at about 12.5". The other toilet flange dimension is only about 14.5" as well.

    Is this wrong? Thanks,


    P.S. - I posted this on the toilet thread but urgently need the answer so sorry for the duplication.
  2. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Nov 8, 2005
    Hansville, Washington
    An interesting paper:

    illustrates why

    claims that "With the superior flushing of the 1.6-gpf water closet, the plumbing codes have prohibited the installation of a double sanitary tee or double fixture fitting for back-to-back water closets." They go on, and say that you can use a double combination wye and a 1/8 bend, or a double sanitary tee at least 30 inches from the centerline of the WC outlet. No explicit mention of the DFF, but it looks like the 30" rule mught apply there as well.

    Disclaimer: I don't have access to an honest-to-God Code book, but it probably doesn't matter. What matters is what your local authority wants.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    I have never seen a prohibition to the standard back to back fixture fitting. A sanitary cross, however, is almost always never permitted. The double Y and street 1/8 bends would normally space the toilet openings too far from the wall.

    Last edited by a moderator: Mar 5, 2014
  5. jaynote1

    jaynote1 Plumber

    Jul 7, 2006
    apprentice and office clerk to a master plumber
    southeastern nc
    good call, hj...i consulted my boss on this one, and his reply matched yours almost word for word...........
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