Water category is the IICRC S500 classification that grades water by how contaminated it is, on a three-level scale, Category 1 (clean source), Category 2 (significantly contaminated), and Category 3 (grossly contaminated), and it drives how aggressively the loss must be handled.
What is a water category?
S500 keys the contamination response to the water's origin and its degradation over time. Category 1 is water from a clean source such as a supply line; Category 2, sometimes called grey water, carries significant contamination that can cause illness, such as washing-machine or dishwasher discharge; Category 3, black water, is grossly contaminated, including sewage and floodwater carrying ground contaminants. The level is not fixed at the moment of loss: clean Category 1 water degrades to Category 2 and then Category 3 as it sits, contacts contaminated surfaces, and grows microbes. The EPA and FEMA both treat floodwater as presumptively contaminated requiring removal of porous materials (EPA, Mold Cleanup in Your Home; FEMA flood guidance). The full S500 text is paywalled, so this is cited at the level public agency guidance supports.
Why it matters to a mold inspection
Category drives scope. Porous materials soaked by Category 3 water generally come out rather than dry in place, while the same material in Category 1 may be salvageable if dried fast. Misclassifying a loss, calling aged or sewage-contacted water "clean," understates the required removal and undercuts the report's defensibility. Category pairs with the water class, which measures evaporation load rather than contamination. See clean water to Category 3 in 72 hours and the water Category 1 vs 2 vs 3 comparison.
MoldMind stores the S500 category, the pathway, and the duration as structured fields, so a category call is documented with the facts that justify it.
Sources
- EPA, Mold Cleanup in Your Home: floodwater is treated as contaminated; porous materials are removed.
- FEMA flood guidance: floodwater carries contaminants and degrades materials it contacts.