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Thread: Double fixture fitting for toilets

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  1. #1
    DIY Member Hazel's Avatar
    Join Date
    Jan 2006

    Default Double fixture fitting for toilets

    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. #2
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
    Join Date
    Nov 2005
    Central Florida


    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.

  3. #3
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default fitting

    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 Terry; 03-05-2014 at 11:56 AM.

  4. #4
    Plumber jaynote1's Avatar
    Join Date
    Jul 2006
    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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