Tree roots are often blamed for damaging sewer pipes and then blocking them. However, root growth into a sewer only occurs where the sewer has first been damaged by other factors. This damage can be due to poor original construction, the aging and cracking of sewer pipes, soil settlement and the subsequent separation of pipe sections, and the failure of pipe grout joints. Roots do not cause this damage.
Tree roots can grow continuously throughout the year, even in a climate with cold winters.
When small, exploratory tree roots come in contact with a leaking or partially collapsed sewer pipe, they are stimulated to grow vigorously, often growing into the damaged pipe. The air, moisture, and nutrients available to tree roots from a damaged sewer pipe stimulate rapid root growth. Research has shown that two types of root growth occur in damaged sewer pipes. Sometimes roots enter the pipe from the bottom and grow along the length of the pipe. Other times roots enter through a crack and grow in a ring around the inside of the pipe occasionally developing into a complete blockage.