Water ResourcesSewer System

Tree Roots vs. Sanitary Sewer Lines

Tree roots growing inside sewer pipes are generally the most expensive sewer maintenance item experienced by City residents. Roots from trees growing on private property and on parkways throughout the City are responsible for many of the sanitary sewer backups and damaged sewer pipelines. Should roots become a problem in your sewer line, consult the yellow pages under the heading, "Sewer Contractors," for companies that perform television inspections of pipes and root control.

roots growing inside sewer

Roots growing inside sewer line

Choose Tree Locations Carefully

Be aware of the location of your sewer service lines, and refrain from planting certain types of trees and hedges near the sewer lines. Consult your local nursery or a horticulture/landscape specialist for advice on tree selection. The replacement cost of a sanitary sewer service line, as a result of damage from tree roots, can be very expensive.

Root Growth in Pipes

Roots require oxygen to grow. They do not grow in pipes that are full of water, or where high groundwater conditions prevail. Roots thrive in the warm, moist, nutrient rich atmosphere above the water surface inside sanitary sewers. The flow of warm water inside the sanitary sewer service line causes water vapor to escape to the cold soil surrounding the pipe. Tree roots are attracted to the water vapor leaving the pipe, and they follow the vapor trail to the source of the moisture, which are  usually cracks or loose joints in the sewer pipe.

Upon reaching the crack or pipe joint, tree roots will penetrate the opening to reach the nutrients and moisture inside the pipe. this phenomenon continues in the winter, even though trees appear to be dormant.

Problems Caused by Roots Inside Sewers

Once inside the pipe, roots continue to grow. If not disturbed, they will completely fill the pipe with multiple hair-like root masses at each point of entry to the pipe. The root masses inside the pipe become matted with grease, tissue, and other debris discharged from the residence or business. Some of the first signs of a slow flowing drainage system are gurgling noises heard from toilet bowls, and observing wet areas around floor drains after completing the laundry. A complete blockage will occur if no remedial action is taken to remove the roots/blockage.

As root continue to grow, they expand and exert considerable pressure at the crack or joint where they entered the pipe. The force exerted by the root growth can break the pipe, resulting in total collapse of the pipe. Severe root intrusion and pipes that are structurally damaged will require replacement.

During drought conditions and in winter, tree roots travel long distances in search of moisture. As a general rule, tree roots will extend up to 2.5 times the height of the tree. Some species of trees may have roots extending five to seven times the height of the tree.