What is the best way to mate a new 2" PVC drain into an existing 3" cast iron bell that is part of the 4"` cast iron vent stack. The previous arrangement was 2" galvanised into the bell, sealed with oakum and lead. I looked at the Fernco thick rubber gaskets but the cast iron bell seems a bit out of round so I am unsure of how effective a seal I can get taking that route.
Thanks.