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Thread: Cast Iron Question

  1. #1
    DIY Junior Member Smunderdog's Avatar
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    Default Cast Iron Question

    I have a 1957 ranch with what I believe to be the original cast iron drain lines. When this was put in, why would they have used 4" pipe run vertically down from the toilets (only about 18" or so), then transitioned to 3" using a 4 x 3 elbow, then run the 3" to the 4" main line?

    Why wouldn't they have just run 3" all the way from the toilet to the main and then transitioned to 4"?

    Just curious more than anything...

  2. #2
    Plumber jimbo's Avatar
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    Hard to say what they were thinking, but to the best of my knowledge, it would never have beeen legal under any code to transition a waste line to a smaller size.

    If this has been working since 1957 without problems, I would be the last one to recommend you go out and change it.

  3. #3
    DIY Junior Member Smunderdog's Avatar
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    Thanks Jimbo - that is what I thought. Has been working most likely because the vertical 4" run is only 18" or so and then the horizontal 3" run is only another 18" before it hits the 4" main. At least it is that way on the one I'm redoing in the near future...

    As part of my project of replacing a good portion of my cast drain lines, I'll be replacing the toilet drain with 3" for the entire run between the toilet to the main...

  4. #4
    Master Plumber-Gas Fitter shacko's Avatar
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    Quote Originally Posted by jimbo View Post
    Hard to say what they were thinking, but to the best of my knowledge, it would never have beeen legal under any code to transition a waste line to a smaller size.

    If this has been working since 1957 without problems, I would be the last one to recommend you go out and change it.
    This is just information: It was a common practice to use a 4x3in closet bend with the cast iron systems. It is still legal under the UPC, the only place that you can do that, that closet bend is also close to a true 90deg. fitting.

  5. #5
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    Give Shacko a cigar Closet bends can be 4" under both the UPC and the IPC And it was very common because it's darn near impossible to find a 3" CI toilet flange.

  6. #6
    Plumber jimbo's Avatar
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    But does anyone maintain that code allowed you to run a few feet of four inch pipe, then transition that to 3" pipe? I am not arguing that it works...he has told us that.

  7. #7
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    I think that's one of dem gray areas.

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default 4x3 bend

    It not only works, but it is legal, and is the only way I have ever done it, other than when we were using all 4", then we used 4x4 closet bends. Plumbers who use 3" toilet risers, in my opinion, are more concerned about how inexpensively they can install it, rather than what is best for the customer.

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