Every case is different, but here was mine. I hired a plumber to replace a bad line. The line left the house at about 4' deep, went across the yard, was about 6' deep at the curb, went to the middle of the street, then straight down an additional 15' to the sewer line. The sewer line had to be broken into, a saddle placed over it, topped with 3 bags of sacrete, everything backfilled and packed, and the street asphalt repaired. No way in hell was it a diy job.