@Andrea The whole thing is pretty much fucked and needs to be completely replaced. Old terracotta piping, not modern plastic stuff.
Old houses are just constant maintenance.
@Andrea At least it does still drain, just not super-well. Means it's not an *urgent* repair. But important, so it needs to be done.
Consider this a friendly, local pub. Make yourself at home, bring your friends, have a good time! Meet new people, have a laugh, enjoy the ambience, and the Oxford commas.