Water categories in plain terms
The water restoration industry's standard, ANSI/IICRC S500, sorts water damage into three categories. Category 1 starts from a clean source, such as a supply line. Category 2 carries significant contamination. Category 3 is grossly contaminated and can contain pathogenic, toxigenic or other harmful agents.
Sewage is the most familiar Category 3 example, and IICRC's 2026 position statement also discusses weather-related flooding. Water can also move to a higher category over time; a clean leak that sits for days in a warm building may not stay clean.
What changes when water is Category 3
IICRC states that Category 2 or 3 water calls for remediation before restorative drying. In practice, that means contaminated porous materials are removed, and non-porous surfaces are cleaned and disinfected, before dehumidifiers and air movers are used to dry the structure.
CDC's floodwater guidance makes the same practical point: discard porous items that cannot be disinfected, and clean surfaces before disinfecting them.
The S500 is a purchasable consensus standard rather than a law, and IICRC has said a revision is under way. We refer to it because it is the common reference point that insurers, adjusters and contractors use when they discuss water categories.
Category 3 events often come with a second problem: time. A flooded building may sit for days before anyone can get in, and every day adds to how far contamination and moisture have traveled. We plan the scope around what we find, not around an assumption that only the visible area is affected.
Our black water process
- Assessment We identify the water source and category, map the wet area and check for electrical and structural hazards.
- Safety and containment Affected areas are isolated from clean areas, and the crew puts on protective equipment.
- Extraction and removal Water is extracted; carpet and pad, drywall, insulation and upholstered items that absorbed it are removed.
- Cleaning and disinfection Remaining surfaces are cleaned to remove soil and then disinfected with registered products per label.
- Drying Drying equipment runs until moisture readings reach dry conditions for each material.
- Verification records You receive moisture logs, photos and a written scope.
Areas commonly affected
- Basements and finished lower levels
- Crawlspaces
- Attached garages
- Drywall, framing and subfloors
- Storage rooms and their contents
- Commercial ground-floor spaces
- First-floor rooms in homes and rental units
Health precautions
CDC warns that floodwater can carry human and livestock waste, and that contact can lead to wound infections, rashes, gastrointestinal illness and tetanus. Avoid wading in contaminated water, wear rubber boots and gloves if contact is unavoidable, and seek medical care for wounds exposed to it.
We do not describe a black water cleanup as producing a sterile building. We remove contaminated materials and clean and disinfect remaining surfaces with products used as directed, then dry the structure.
Before you go back in
- Wait for authorities to say it is safe to return after a flood.
- Do not turn on electrical equipment that got wet.
- Photograph damage and keep receipts for any emergency purchases.
- Throw away food that touched contaminated water.
- Keep children and pets out of affected areas.
Specialists and insurance
Electrical inspections go to an electrician, structural concerns to a contractor and widespread mold growth to a mold remediation professional. Coverage for flooding and sewage often differs from coverage for other water losses, so check with your agent before assuming either way. For sewage from inside the building, see sewage backup cleanup; for business properties, commercial sewage cleanup.