Water Damage Categories and Classes Explained

Updated October 2026. General information, not legal, insurance or engineering advice.

Water categories

• Category 1: water from a sanitary source, such as a broken supply line or an overflowing sink with clean water.
• Category 2: significantly contaminated water, such as washing machine or dishwasher discharge. It can cause illness if consumed or exposure is prolonged.
• Category 3: grossly contaminated water, including sewage, river flooding and rising ground water. It is treated as a health hazard.

Category can worsen with time. Clean water that sits for days on dirty surfaces can become Category 2 or 3.

Damage classes

• Class 1: least moisture, only part of a room, low absorption materials.
• Class 2: whole room carpeted, moisture in walls up to about 24 inches.
• Class 3: water from overhead, walls, ceilings, insulation and carpet saturated.
• Class 4: deeply held moisture in dense materials such as hardwood, concrete and plaster, needing specialty drying.

Where this comes from

These terms come from the ANSI/IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration, published by the Institute of Inspection, Cleaning and Restoration Certification. Reputable companies follow it. Ask yours which category and class they assigned and why.

Sources and further reading

• IICRC: Standards and certified firms

Related services

• Sewage Backup Cleanup
• Water Extraction and Flood Cleanup

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