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Sewage Backup in the House or Basement: What to Do First

Sewage coming up through a floor drain, tub, shower or toilet is a health problem as well as a water problem. Here is what to do first, who to call, and what usually cannot be saved.

Updated November 2026 · 6 min read

Quick answer

Stop using water in the house, keep children and pets out, and don't touch the water without rubber boots, gloves and goggles (CDC). If neighbors are backing up at the same time, the public sewer is likely full, so call your city's public works or sewer utility (MMSD). Sewage is Category 3 water, so cleanup is a job for a professional crew (IICRC).

What should you do first when sewage backs up?

  1. Stop running water. Don't flush, shower, or run the washer or dishwasher. Water you use in the house has nowhere to go and comes back up at the lowest drain (MMSD).
  2. Keep people and pets away. The CDC advises keeping children and pets away from the area until cleanup is done (CDC).
  3. Stay out of standing water near outlets or equipment. If water is near electrical outlets, cords or appliances, don't wade in. Turn off power at the panel only if you can reach it while standing somewhere dry.
  4. Photograph everything before anything is moved or thrown out, for your insurer.
  5. Call your sewer utility if it may be the public line, and a restoration company for cleanup.

Is it your line or the city's sewer?

The pipe that carries wastewater from your house to the public sewer main is called the lateral, and maintaining it is usually the homeowner's responsibility. Where the homeowner's part ends varies by community, so check with your city (MMSD).

  • Backup in dry weather: there's a good chance your own lateral is clogged (MMSD). A plumber clears it.
  • Backup during heavy rain, and neighbors have it too: the public sewer is likely full. Call your city or village public works right away (MMSD). FEMA notes that sewer systems can overflow during heavy rainfall, especially in urban areas (FEMA).
  • Even in rain, a clogged lateral can still be the cause (MMSD), so a plumber may need to check it with a camera.

Each WaterRemoval247 town page lists the local sewer or wastewater number to call.

Water still coming in or standing? A local restoration company can start water removal now.

Call (866) 217-4054

Why is sewage cleanup a job for professionals?

Sewage is Category 3 water. It can carry harmful bacteria and viruses, and the industry standard calls for contamination controls and protective gear (IICRC). See clean, gray and black water for how the categories work.

If you must be near it, the CDC says to wear rubber boots, rubber gloves and goggles, and to wash clothes that touched sewage in hot water and detergent before wearing them again (CDC; CDC floodwater guidance).

What has to be thrown out after a sewage backup?

  • Drywall and insulation that sewage touched. The CDC says to remove and discard them (CDC).
  • Things that can't be cleaned or dried quickly, such as mattresses, carpet and pad, rugs, upholstered furniture, stuffed animals, baby toys, pillows, books and paper (CDC).
  • Hard surfaces such as concrete, tile and sealed wood can usually be cleaned and disinfected. Never mix bleach with ammonia or any other cleaner (CDC).

Photograph and list what's thrown out before it leaves the house. Your adjuster may ask for it.

How much does sewage cleanup cost?

Angi's cost data puts black water cleanup, which includes sewage, at about $7.50 per square foot, compared with about $3.50 for clean water. For a basement, two feet of sewage backup can cost $2,800 or more (Angi).

See the water damage restoration cost guide for the full breakdown.

Does homeowners insurance cover sewer backup?

Usually not on a standard policy. Sewer backup isn't covered by a typical homeowners policy or by flood insurance. It has to be bought separately or added as an endorsement (Insurance Information Institute).

When you report the claim, describe what happened rather than calling it a flood. "Flood" can have a specific meaning to insurers, and causes like sewer backup or sump pump failure may be handled differently (Michigan DIFS). More detail: does homeowners insurance cover water damage?

How do you keep sewage from backing up again?

  • Ask a plumber to camera-inspect the lateral if it has been clogged before. Tree roots growing into cracks are a common cause (MMSD).
  • Ask about check valves or backflow preventers. FEMA lists them, along with a backup sump pump, as ways to reduce basement backup (FEMA).
  • If your basement is finished, ask your agent what a sewer backup endorsement would cost.

Common questions

Can I clean up a small sewage backup myself?

The industry standard treats sewage as Category 3 water that needs contamination controls and protective gear. If you have to be near it, the CDC says to wear rubber boots, rubber gloves and goggles. Anything porous it touched, like drywall, carpet and insulation, has to go.

Who pays if the city sewer caused the backup?

It depends on your city and your policy. Report it to your sewer utility right away and ask how it handles damage claims. Many homeowners policies only cover sewer backup with an endorsement.

Why does sewage come up through a floor drain or tub first?

When the lateral or public sewer can't carry water away, it backs up through a floor drain, sink, toilet or other fixture, and the lowest one in the house overflows first.

How much does sewage cleanup cost?

Angi's cost data puts black water cleanup, which includes sewage, at about $7.50 per square foot. Two feet of sewage in a basement can cost $2,800 or more.

Is it safe to stay in the house?

Keep children and pets away from the affected area until cleanup is finished. If the backup is large, the smell is strong, or the water is near electrical equipment, stay out of that part of the house.

Related guides

Local water damage help

Each state page lists the towns we cover, with local shut-off and sewer numbers and flood notes.

Town pages that cover this problem, with local water and sewer numbers:

Sources:

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