Your Main Sewer Line Is Backing Up: What to Do Right Now

Published July 15, 2026 · Snake-It-Away Inc.

A main sewer line backup is one of the few plumbing problems that can genuinely damage your home in a matter of hours. If sewage is coming up through a floor drain or multiple fixtures are backing up at once, act quickly. Here's what to do right now.

First: how to know it's the main line (not just one drain)

It's likely a main-line problem if:

• More than one fixture is backing up at the same time
• The lowest drain in the house (usually a basement floor drain) is where water comes up
• A toilet gurgles when you run a sink or the washing machine
• Water backs up when you flush or drain elsewhere

One clogged sink is a local problem. Several fixtures at once means everything is hitting a blockage in the main line to the street.

Do this now

1. Stop running water. No sinks, no showers, no laundry, no dishwasher. Every gallon you send down has nowhere to go but up.
2. Don't flush. Each flush adds to the backup.
3. Keep people and pets away from any standing sewage. It's a health hazard.
4. Shut off water to a continuously running fixture if one is stuck.
5. Call for professional help. A main-line backup won't clear itself, and store-bought products won't touch it.

Do NOT do this

• Don't pour chemical drain cleaner into a standing backup. It won't clear a main line and you'll be dealing with caustic water.
• Don't keep plunging a toilet that's part of a whole-house backup. The blockage is downstream.
• Don't wait until morning if sewage is actively rising. This is what 24/7 service is for.

What causes a main-line backup

Usually one of three things: tree roots in an older line, years of grease and debris buildup, or a pipe problem like a collapse or sag. A camera inspection tells us which, so we fix the actual cause and not just today's symptom. If the line itself is cracked or collapsed, we handle the sewer line repair too.

Why fast matters here

Sewage backing up into a finished basement causes real, expensive damage. The faster the line is cleared, the less that reaches your floors. That's why we answer the phone around the clock.

Call Snake It Away right now at (781) 858-8314. We're Medford-based, family-owned since 1997, and available 24/7 for emergency drain and sewer service across Boston, Medford, Somerville, Revere, and the surrounding towns.