A little known fact about roots is that they will travel long distances when water is scarce, such as during droughts and in winter months. When shrubs and trees get thirsty, they follow moisture vapors that escape through small cracks or poorly-sealed joints in sewer and water lines, penetrating the pipe.
Plant root systems are comprised of large, permanent roots used to support and stabilize, and smaller, temporary feeder roots. These smaller roots are what absorbs water and nutrients. Most roots sits in the top 6-18 inches of soil, where they can access the nutrients, oxygen, and water needed for the plant to grow. How quickly the plant grows depends on factors such as soil depth, aeration, water supply, temperature, and mineral supply.
To reliably calculate how far out a root system stretches, you can estimate that roots typically extend two to three times the height of the tree, though they can reach as far as seven times the tree’s height. Larger, more mature trees may have up to thousands of feet of root system. Roots are usually more far reaching in well-drained or sandy soils than in clay soils.
If left unchecked, the roots can fill the pipe entirely in hair-like masses at each entry point. These root masses then trap grease, toilet tissue, and other debris flowing from homes and businesses down to the main sewer. The end result: slowed drains and reduced sewer flow. If the roots are not removed and their growth is left unchecked, a complete blockage can occur.
Once roots have made their way into the pipe, they grow and expand, which puts pressure on and widens their entry point. This often results in the breaking of the pipe and can result in the total collapse, which then must be fixed or replaced entirely.
Some pipe materials are more accessible than others for root intrusion. Clay tile pipe is easily invaded and damaged by tree roots. Concrete piping and PVC pipe may also be penetrable, but are sturdier than clay pipe. PVC often has fewer joints, and the tight-fitting nature of its joints makes it less likely to leak.