Hello, I am replacing my shower membrane pan with a new one. I have purchased a cast iron drain to replace the old cast iron one, however where ever I read about doing a shower pan they say to replace with PVC drain. Is this something that must be done? Or can I replace it with the same type of drain that was there? How do I seal the drain around the membrane?

Thanks!

The flange of the cast iron drain should be intact in the floor, flush with the floor, and reusable. You may choose to use the top parts of the new cast iron shower drain.
The top flange bolts to the bottom flange and clamps to seal.