Sewage Backup in the House: First Steps and When It Is a Biohazard
Water that came from a toilet, floor drain or sewer line carries bacteria and viruses, and EPA guidance treats anything soaked by it as contaminated. Drywall, carpet and insulation it reached generally have to be removed, not just dried.
The first hour is about stopping the flow and keeping people out. The cleanup itself is a job for a crew with protective equipment and the right disinfectants.
If this is unsafe or getting worse right now, don't wait — send an emergency request and it's flagged for priority routing to an independent local pro.
What to do in the first 5 minutes
- Stop running water and flushing toilets anywhere in the house.
- Keep children, pets and anyone with a weakened immune system out of the area.
- If water is near outlets or appliances, shut off power to that area at the breaker only if you can do so from a dry spot.
- Call a plumber to clear the line and a remediation crew for cleanup.
- Photograph the damage and call your insurer.
Do not do this
- Do not walk through sewage water without boots and gloves.
- Do not use fans to dry a sewage-soaked room before cleaning; they can spread contamination.
- Do not keep soaked carpet, pad or mattresses.
What's likely going on
Blocked main sewer line
Roots, grease or a collapsed pipe; every fixture backs up at the lowest drain.
Municipal sewer overload during storms
Heavy rain can push sewage back through floor drains; a backwater valve helps prevent repeats.
Failed septic system
A full or failed tank backs up into the home and needs pumping and inspection.
What it typically costs
HomeGuide's third-party estimate for biohazard cleanup is $25 to $150 or more per hour, or $1,500 to $5,000 for most jobs (HomeGuide). Sewer backup coverage is often an add-on endorsement, so check your policy.
Frequently Asked Questions
Is a sewage backup covered by homeowner's insurance?
Often only with a water backup endorsement. Check your declarations page or ask your agent before cleanup starts.
Can I clean up a small backup myself?
A small, contained spill on a hard floor can be cleaned with protective gear and disinfectant. Anything that soaked into porous materials should be handled by a professional.
How do I prevent another backup?
A plumber can clear blockages and inspect the line; for homes on municipal sewer, a backwater valve keeps floodwater from pushing back through the drains.
The service that handles this
Guidance only — independent local providers assess and price their own work. Last reviewed: October 16, 2026.
Sources for the cost figures
- HomeGuide: Biohazard cleanup cost (third-party estimate) (third-party estimate)
- EPA: Flooded homes, cleanup and safety
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