Sewer main under concrete slab foundation

Hello, I am new to the forum and new to home improvement. I have an unfinished basement that I would like to add a bathroom to. I have cut a hole, dug and located the 4" cast iron main that the upstairs main feeds into. My question is, can I connect to this underground main with ABS pipe or is cast iron required under concrete slab? The soil I have encountered is like clay with very little rock and not much moisture. Any help would be greatly appreciated.

ABS is allowed underground as I understand it, but you'd need to check with the local authorities to see if they allow it. Snap the cast iron with a rented snap cutter, then use a fernco connector to patch in the fitting and new pipe. You need to maintain 1/4" per foot for the new stuff to that point.

Thanks for your input. I am trying to avoid a nightmare re-do.

A vent might be needed for the toilet too.