A few years ago, oh.. I think probably 6 or 7 years ago, I fixed the
plumbing of this toilet in a rental I owned. Or so do I think. This
is the downstairs unit of a two family house which was built in the
1940's, it not earlier.

The lead bend on the waste pipe was leaking. I removed the toilet.
Chipped out a portion of the mosaic tile foor to get to the lead bend.
I did not remove the lead bend completely. Just saw cut it and left
a stub hanging out from the branch of cast iron stack. Then I wrapped
the stub with a rubber connector with stainless steel straps and
connect the upstream end with PVC pipe and bend. I took the
opportunity to retile the bathroom with 8x8 ceramic tiles also.

Six or seven years later tenants are complaining the toilet is
difficult to flush. But the rubber connection I made still hold as
there is no leak. So after eating turkey I am going to remove the
toilet to see what may have caused the plug as the tenants have gone
home for the holiday.

Anyone has this experience or care to speculate what I may find?