Check out the roots our service techs found in the pipes of a hotel in Hillsboro, OR!
The easiest way for a tree root to find and infiltrate a sewer line is a crack in a pipe. This sends a signal to the tree that it can find water and oxygen in your sewer line. It also makes it easy for the roots to get in.
You can spread copper sulfate (rock salt) and potassium hydroxide on the ground where your sewer lines are located. These chemicals will discourage tree roots from growing near your pipes.