Sewage on the floor of a living space. Category 3 water, and not yours to clean
Sewage is Category 3 water under the IICRC S500 standard, grossly contaminated and able to cause significant harm if contacted, and wet materials start growing mold in 24 to 48 hours.
What is probably happening
- A backed-up toilet, floor drain or waste line is sewage, whatever it looks like. The S500 standard classes it as Category 3 regardless of color.
- Anything porous that it touched (carpet, padding, drywall that has gone soft, upholstered furniture, rugs, cardboard) gets removed and thrown out, not cleaned.
- The plumber fixes the cause. The restoration or biohazard crew removes contaminated material, disinfects, and dries.
Do this in the next five minutes
- Stop using water in the house so nothing more goes down the drains.
- Turn off power to the room at the breaker if water is near outlets or cords.
- Open windows and doors to move air.
- Take photos from the doorway for the insurance claim.
- Call a plumber for the blockage and a restoration or biohazard company for the cleanup. Both today.
- Wash your hands with soap and water after any contact, and launder any contaminated clothing separately in hot water.
Do not
- Do not mop it up and carry on. Sewage carries bacteria and viruses, and porous materials it touched need to go.
- Do not run a fan into the rest of the house. You want air out, not around.
- Do not wait more than a day. The EPA says mold can grow on wood, drywall and carpet that stays wet more than 24 hours.
Who to call
A water damage restoration company that handles Category 3 water
Sewage cleanup is Category 3 water restoration under IICRC S500; a plumber stops the source but does not remove and dispose of contaminated materials.
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What it should cost
$2,000 to $10,000 per project
Fixr sewage backup project range; Angi puts black water restoration at $7.50 per square foot
Source: Fixr, biohazard cleanup cost, 2025, and Angi, water damage restoration cost, August 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the water damage page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Are you assigning this as Category 3 water under S500, and will the written scope say so?
- What will be removed and disposed of, and what will be disinfected and dried in place?
- Will you leave daily moisture readings and a drying log?
- Are you asking me to sign an Assignment of Benefits, and what happens if I do not?
- Is the plumbing repair in this quote, or is that a separate contractor?
End the call if
- A quote to clean and dry carpet and padding that sat in sewage rather than remove it.
- No written scope, or an Assignment of Benefits pushed at you on the spot.
- Cash only or a large deposit up front.
Where this comes from
- IICRC, S500 category of water position statement, 2026
- CDC, guidelines for cleaning safely after a disaster
- Washington State Department of Health, cleaning up sewage spills
- US EPA, flood cleanup to protect indoor air and your health
- Texas Department of Insurance, home insurance guide
- Fixr, biohazard cleanup cost, 2025
- Angi, water damage restoration cost, August 2026