How do you connect cast iron to PVC?
Then, can you glue PVC to cast iron?
You can't glue PVC to cast iron. What you have there is a 4" cast iron hub. There is a flange that should fit your needs. It's made in PVC or ABS.
Regarding this, how are cast iron drain pipes joined together?
DWV or drain waste vent pipe. These cast iron pipes have a “bell” or “hub” on one end and the smaller end of another pipe fits into it. The “joint” is then packed with a product called oakum. Then topped off with molten lead to seal the joint and prevent movement and possible future leaks.
Cast iron pipe prevents the spread of fire much better than plastic pipe because cast- iron is not combustible. On the other hand, combustible pipe such as PVC and ABS, can burn away, creating an opening through which flames can move from one part of the building to the next.