Water Category & Class Helper
Look up what your water loss is in IICRC terms — the Category (how contaminated) and the Class (how much water) — to understand the drying difficulty and how it must be handled safely.
Calculator
Category 1 — clean water. Water from a sanitary source (supply line, rain, melting snow). Least hazardous, but it degrades to Category 2 within ~48–72 hours. Class 2 — large area: An entire room with carpet and cushion, water wicked up walls under ~24 in. The IICRC Category rates how contaminated the water is; the Class rates how much water and how hard it is to dry. This is a reference classifier, not medical advice.
The IICRC S500 standard describes a water loss on two independent axes. The Category rates how contaminated the water is (1 clean, 2 gray, 3 black) and drives the safety and removal decisions. The Class rates how much water is present and how hard it is to dry (1 through 4), and drives the drying equipment. Knowing both is the fastest way to understand a restoration quote — and to know when a job is a health hazard rather than a mop-up.
Formula
This is a reference classifier rather than an arithmetic formula: pick the Category and Class that match your situation and the helper returns the IICRC definition and its drying implication.
Worked example
A washing-machine overflow that soaked a whole carpeted room is typically Category 2 (gray water), Class 2 (large area): contaminated enough to need protective equipment, and wet enough that the carpet, pad and lower walls all need aggressive drying. Left more than 48–72 hours it can degrade toward Category 3.
Category drives safety, Class drives drying
The two axes answer different questions. Category answers “is this water dangerous?” — Category 3 black water (sewage, flood, ground water) is a health hazard where porous materials are removed and certified pros with PPE do the work. Class answers “how big is the drying job?” — a Class 4 specialty situation with water bound into hardwood or concrete needs methods a Class 1 spill never does.
Clean Category 1 water does not stay clean: without fast drying it degrades to Category 2 within about 48–72 hours as it picks up contaminants and feeds microbial growth. This helper is a reference, not medical advice — for any health concern, see a physician or your local health department.
Reference table
| IICRC water category | What it means |
|---|---|
| Category 1 — clean | Sanitary source (supply line, rain). Degrades to Cat 2 within ~48–72 hrs. |
| Category 2 — gray | Significant contamination (appliance overflow, sump failure). Can cause illness on contact. |
| Category 3 — black | Grossly contaminated (sewage, flood, ground water). Health hazard — certified pros only. |
| IICRC water class | How much water |
|---|---|
| Class 1 — least water | Small area, low porosity, minimal absorption. Fastest to dry. |
| Class 2 — large area | A whole room with carpet and cushion; water wicked up walls under ~24 in. |
| Class 3 — greatest water | Water came from overhead — saturated ceilings, walls, insulation, floor. |
| Class 4 — specialty | Deeply held water in hardwood, plaster or concrete; needs special methods. |