What Causes Tree Roots in Sewer Lines (and How to Stop Them)

By Sewer Line Repair Team · September 2026 · Marlborough, MA

Tree roots are the number-one cause of sewer clogs we see in Marlborough. But the common story — roots ‘breaking’ the pipe — has it backwards.

How it really happens

Every pipe joint, and every hairline crack, leaks a tiny vapor plume of moisture and nutrients. Root tips — finer than hair — follow that plume and slip through gaps as small as a millimeter. Once inside, the feast begins: roots branch explosively, catching paper and waste until flow chokes off.

Which pipes are vulnerable

Clay tile with its many joints is the classic victim; cast iron with corroded joints is next. Even PVC can suffer if a joint was poorly glued or shifted by settling soil.

Which trees are worst

Willows, maples, oaks, and elms are aggressive seekers — all common in Marlborough yards. But any tree within 20–30 feet of a compromised joint is a candidate.

The permanent fix

Cutting roots restores flow for a year or two. Lining the pipe eliminates every joint and crack roots could enter — a jointless pipe is root-proof. That’s the difference between a $300 recurring haircut and a once-and-done cure. Call (833) 713-2101 and we’ll show you your roots on camera, then quote both options honestly.

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