What are the common causes of a sewer line backup?

The common causes of a sewer line backup are tree root intrusion, grease buildup, flushing wipes or other non‑flushables, scale and sludge narrowing the pipe, and damaged or sagging sections that trap waste. The most frequent trigger our plumbers see is roots finding tiny cracks, then expanding until the line can’t drain. If only one sink is slow it’s often a local clog, but if the lowest drain backs up when an upstairs fixture runs, the main line is obstructed. A camera inspection confirms the exact cause; cleaning may restore flow, while cracked or collapsed pipe usually needs trenchless repair or excavation. We handle these issues throughout the Denver metro, including Westminster homes. We also offer hydro jetting and trenchless options, with emergency service available.

Watch for these decision signals:

• Multiple fixtures backing up together
• Gurgling at a floor drain or the lowest shower
• Sewage at an exterior cleanout or strong sewer odor indoors
• A toilet flush sending water into a tub or shower

Limit water use and avoid flushing until a licensed plumber inspects the main with a camera.

Updated: 2026-05-09

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