Sewage or floodwater: do not clean this yourself
The EPA is direct: if the water or mold damage was caused by sewage or other contaminated water, call in a professional. This is a biohazard before it is a mold problem.
What is probably happening
- A sewer backup, toilet overflow that ran for a while, or outside floodwater that carries bacteria and whatever was in the street.
- Anything porous it touched (drywall, carpet, padding, insulation, upholstery) is contaminated and comes out. The EPA says absorbent materials may have to be thrown away.
- Mold on top of that is expected. It is handled as part of the same cleanup, after the contaminated material is gone.
Do this in the next five minutes
- Stop the source: close the main valve for a plumbing failure, or wait for the outside water to recede.
- Open windows. Do not run the HVAC if water or mold reached ducts or the air handler.
- Photograph everything before anything is moved.
- Call a restoration company that handles Category 3 (black water) work today. Ask for that phrase.
- Call your insurer today. Sewer backup is often a separate rider. Ask whether you have it.
Do not
- Do not scrub sewage mold with bleach and call it done. The EPA does not recommend biocides as routine practice, and the contaminated material has to leave the house.
- Do not keep carpet or padding that sewage touched.
- Do not let a mold only contractor take the job. The contamination comes first.
Who to call
A restoration company rated for black water, or a biohazard cleanup firm
Sewage cleanup is a category of water damage work with its own protective gear and disposal chain. Mold removal is a step inside it, not a separate call.
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What it should cost
$7.50 per sq ft
Black water cleanup. Clean water runs $3.50 and gray water $5.25 per square foot. If mold has set in, add $1,200 to $3,800
Source: 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 treating this as Category 3 water, and what changes because of that?
- What gets removed and disposed of, and who hauls it?
- Will you dry and meter the structure before any mold work starts?
- Is antimicrobial treatment part of the scope, and what product?
End the call if
- A plan that dries carpet and padding that sewage touched instead of removing it.
- No mention of protective gear or disposal.
- A mold air test sold before the sewage is out.