I just had a plumber repair my 4" waste line, which was cast iron.
He replaced a 10' section with ABS.
At the end that transitioned from ABS to Cast Iron he used a coupling specifically designed for that (part # 3000-44, labelled '4" Cast Iron to 4" Plastic" - see first photo). However at the Cast Iron to ABS transition it appears he used a regular no-hub coupling (see second photo). (My reference direction is the direction of water flowing downhill).
I tried to ask him why, but I didnt get an answer. I want to give him the benefit of the doubt, but I also want a fix that doesnt fail early.
Question: is there any reason why one would use a '4" Cast Iron to 4" Plastic" coupling at the 'ABS to cast iron' joint, but not at the 'cast iron to ABS' joint?
It's possible I'm mis-identifying the connector on the 'cast iron to ABS' joint - see photo below. That's not a "CI to PL" coupling, right?