Root intrusion at a joint or crack is the most common cause we see, especially in an older line near mature landscaping. Beyond that, a section of pipe can settle unevenly over years and develop a low spot, called a belly, where waste and paper collect instead of flowing through, and a joint can simply separate slightly with ground movement over time. Each of these produces a similar symptom, slow or backed-up drainage across multiple fixtures at once, which is exactly why a camera inspection matters before any repair starts.
Guessing at the cause and digging blind wastes both money and yard. A camera tells us the exact location and the actual defect first, and it also tells us whether the pipe is a good candidate for a trenchless repair or genuinely needs to be dug up, which is a conversation we’d rather have with footage in hand than a guess before anyone breaks ground.