Poster #11 some of us remember your alter ego vinn. :LOL: :LOL: a pendant is just a hanging thing. To be called pedantic is not an insult, neither is narcissistic , which you are.
I had the same problem - the magnet test showed it up . Cutting out the pipe showed a solid part blockage that required poking out with a metal rod. Flushing/chemicals wouldn't touch it.
If there is another wc into the stack on a floor above, you have a Single Stack and the 450 is to stop a higher discharge interfering with the lower wc connection . If no connections I would argue against it with B.C ;)