When the Roto-Rooter man tells you your sewer pipe is clogged with tree roots and you need a sewer cleaning, what exactly does he do? Usually he will begin by feeding a small cable with a sharp blade on the end to bore through the clog and allow it to drain. Next, he will use a larger cable machine with a 4-inch or 6-inch c-shaped blade on the end. The blades are spring loaded and are gently squeezed so they fit into the pipe. Once inside, they spring outward and hug the pipe wall.
When the machine turns on, the blades spin and shave the pipe walls of all debris and roots that have penetrated the sewer pipe at the pipe joints or through cracks. The old Roto-Rooter ads bragged of shaving your pipes "Razor-Kleen." Sewer cleaning can be time consuming and tedious but it's very effective and will keep roots at bay for about a year in most cases.
If the plumber pulls out the cable and notices mud on it, that indicates a serious break in the pipe. The technician will suggest a video inspection using a remotely operated camera. He will show you the condition of the pipe live on a TV monitor and present you with sewer repair options and estimates.