My sewer service line backs up about once or twice a year. When the plumber comes to unblock it, he finds tree roots in the line. The thing is, the only tree that has grown over the line was cut down at least eight years ago, before I moved into the house. The stump has been ground out and there is no evidence above ground that there was a tree there.
The plumber says this is not unusual for the roots of a tree to keep growing after the tree is removed, but he hadn't seen one last that long. Cleaning up after a backup is a pain, so I'm wondering if there's anything else that can be done to ameliorate the situation, short of replacing the line or digging up the yard in search of these roots.