On Aug 16, 5:59 pm, fred wrote:

One of my (tenement) neighbours has had one done recently and a section
of CI was cut out and a plastic branch grafted in with those universal rubber
couplers. Not the tidiest of solutions but it was a new bathroom so should
have been BC assessed.

For the record, I checked with building control and this isn't allowed
in Edinburgh.
You must 'maintain the integrity of the cast iron stack'.
That's Edinburgh for ya.