The IICRC Water Damage Categories
The IICRC S500 standard classifies water by contamination level. Category 1 (clean water) from sanitary sources poses no immediate health risk. Category 2 (gray water) may contain chemicals, biological contaminants, or physical irritants. Category 3 (black water) is highly contaminated — sewage, flood water, or water that has been stagnant long enough to harbor significant microbial growth. Category 1 can become Category 2 or 3 over time if not addressed.
Common Sources of Category 2 Water
- Dishwasher overflow or discharge line backup
- Washing machine overflow (wash water, not supply line)
- Toilet tank overflow (not toilet bowl water)
- Sump pump failure (water that has pooled and may have picked up contaminants)
- Clean water that has been left standing for 24 to 48 hours at warm temperatures
How Category 2 Affects the Restoration Process
Category 2 water requires additional precautions compared to Category 1. Porous materials that absorbed Category 2 water — carpet, padding, drywall below the water line — are typically treated as non-salvageable by professional restoration standards. Hard surface materials can be cleaned and disinfected. Workers require additional PPE. Category 2 water that remains undisturbed for 24 to 48 hours at room temperature is reclassified as Category 3.
Find Local Help
WaterDamageSource is an educational resource. Always consult a licensed professional for guidance specific to your situation.