If not disturbed, the roots will completely fill the pipe with multiple hair-like root masses at each point of entry. The root masses quickly become clogged with toilet tissue, grease and other debris flowing from homes and businesses to the main sewer, resulting in reduced flow and slowed drains. A complete blockage may occur if the roots are not removed and root growth impeded.
Once roots have entered the pipe, they continue to grow and expand, exerting considerable pressure at the crack or joint. The increased pressure often breaks the pipe and may result in total collapse, which requires repair or replacement.
Some pipe materials are more susceptible to root intrusion than others. Clay tile pipe is easily penetrated and damaged by tree roots. Concrete pipe and PVC pipe may also allow root intrusion, but to a lesser extent than clay pipe. PVC pipe usually has fewer joints and because those joints are tightly fitted, they are less likely to leak as a result of settlement around the pipe.