Connection ABS drain directly to cast iron pipe

Discussion in 'Shower & Bathtub Forum & Blog' started by fkshiu, May 21, 2006.

  1. fkshiu

    fkshiu New Member

    May 21, 2006

    I am planning to installing the Schluter Kerdi shower system in my basement shower remodel. After removing all of the old drain hardware the shower stall area, I discovered that the old cast iron drain pipe stub was the perfect height for the Kerdi drain.

    The drain has a 2" ABS solvent weld-on fitting. It slips perfectly over the 2" cast iron pipe.

    My question is can I attach the ABS drain DIRECTLY to the cast iron pipe???

    I am aware that you can use a Fernco-type adapter to go from cast iron to ABS, but that would involve having to cut the cast iron down a bit and installing a section of ABS to attach to the drain. I was wondering if you could somehow attach the ABS drain directly onto the cast iron pipe?

    Is it possible or just a pipe dream??? :p

    Last edited by a moderator: May 22, 2006
  2. Cass

    Cass Plumber

    Nov 12, 2005
    Pipe dream. they shouldn't fit like that if they are the same size. Measure them.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona


    Lots of things look like they should fit together, but do not. This is one of them. There is no way to make a joint between an ABS fitting and cast iron pipe. In fact from the description of your base, I would not use a glued drain fitting anyway. I would use one with a rubber compression gasket that installs from inside the shower base.
    Last edited by a moderator: May 22, 2006
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The Kerdi drain is a special application - Kerdi is a tileable waterproof membrane applied on top of the preslope, then tiled. You must attach the membrane to the special Kerdi drain via thinset, there is no clamp. So, you must make the plumbing connection to the drain through either abs or pvc (depending on which type you buy). I think the only acceptable way to do this would be to tear out the CI p-trap and replace with pvc.

    Attached Files:

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