The CI probably transitions to clay a short distance out side of your foundation.
Lakee, I hate to say this but I'd see about getting a camera over there to have a look see at this line and locate your points of interest as well as inspect the balance of the line.
It's called working smarter not harder!
Use a banded coupling that is properly sized for the 4" to 6" transition.
Also make sure that part of your work is installing an outside cleanout that can run in both directions... essentially opposing wye's and 45's to the surface.