What are the common causes of a sewer line backup?

Common causes of a sewer line backup are blockages in the pipe, structural defects, or excess inflow that overwhelms the line. The most frequent trigger is tree-root intrusion, which squeezes into joints and traps debris until flow stops. Backups range from slow drains to sewage in fixtures; they’re serious when waste comes up at the lowest drain. On camera, early roots often look like fine hair at a single joint before they mat. In the Denver metro, including Arvada, many older lines are more prone to joint gaps and settling.

Look for these other typical causes:

• Grease, fats, wipes, and hygiene products that harden or snag.
• Scale and sludge buildup that narrows the pipe interior.
• Offsets, bellies, or collapses from soil movement or age.
• Storm or groundwater infiltration that overloads the main.

If sewage is backing up indoors, stop water use and call a licensed plumber immediately.

Updated: 2026-03-14

Need help in Arvada, CO? Call (720) 577-4266 or book online.