Hi All,
The past couple of days I've been digging to uncover a problematic area in my sewer line. Approx 30" away from the edge of the house 5-6 feet below grade, I uncovered 6" clay pipe that comes from the house and turns in about a 3 foot radius sweep towards the street. The thing is, they used a 90 degree and a 45 degree fitting to make the 90 degree bend, thus the 90 and 45 do not fit together. It should have been two 45's. There is a 2" diameter root entering the pipe there. I'll take a photo later and post it.

Inside the house I have coming down the main stack, 4" cast iron, 4" PVC, then 4" cast iron again, then it exits the house and somewhere between there and 30" outside the foundation, it transitions to 6" clay.

I'd like to replace everything from the PVC coming down the stack to the 6" clay headed towards the street. How and where do you speculate is the existing 4" cast iron transitioned to the 6" clay?

I'd like to cut out the cast iron and push through a 4" PVC through the foundation in the existing pipe (assuming it is all 6" clay) and through to the thirty inches of pipe entering my hole, make the 90 degree bend and then transition to clay as it heads to the street. I'll add a cleanout there as well.

What is the best way to make the transition from 4" PVC to 6" clay? When I backfill, should I fill with sand or gravel or dirt?