Replacing a 4" cast piping with a plastic. What size of plastic can be used?

Please explain what you're attempting to do or replace. A 4" floor drain with a PVC one? Or do you just wish to convert from cast iron to PVC? Regards, Tom

The 4" cast drainage pipe is buried under the craw space of the house. The pipe was cracked from the the inlet above grade to the where it goes under the house foundation. I will replace all the plumbing for the entire house with plastic. Again the question is, can I run all 3" pvc from the point of the transition from 4" cast to 3" pvc?

The 4" cast drainage pipe is buried under the craw space of the house. The pipe was cracked from the the inlet above grade to the where it goes under the house foundation. I will replace all the plumbing for the entire house with plastic. Again the question is, can I run all 3" pvc from the point of the transition from 4" cast to 3" pvc?
Yes you may. Use a 4" No-Hub Clamp and a PVC 4 X 3" reducing bushing, (I would suggest using a 4 X 2" reducer and running a 2" floor draim.) to convert to PVC. Regards, Tom