Category 1, 2 and 3 water: how dirty was the water?

In plain English

The water-damage industry sorts water by how contaminated it is, judged by where it came from and what it picked up on the way. The category decides how much can be dried and kept and how much has to be thrown away, and it is the first thing on most restoration estimates.

Category 1 starts out sanitary: a broken supply line, a clean sink or tub overflow, an appliance supply hose, rain or melting snow. Category 2 carries enough contamination to make people sick: dishwasher or washing-machine discharge, a toilet overflow with urine but no feces, groundwater seeping in under pressure, a broken aquarium. Category 3 is grossly contaminated and can carry pathogens or toxins: sewage, backflow from beyond a trap, seawater, rising rivers and streams, and wind-driven rain from storms.

Water gets worse with time and warmth. Clean water that sits, or runs into a building that was already contaminated, can become Category 2 or 3 as microorganisms grow; a bad smell is one sign. Hazardous materials (asbestos, lead and the like) don't change the category, but they need qualified people, and the S500 says visible or suspected mold should follow the S520 mold standard and be dealt with before drying.

Key points

• Category 1: sanitary source (supply line, clean overflow, rain).
• Category 2: significant contamination (appliance discharge, urine-only toilet overflow).
• Category 3: grossly contaminated (sewage, seawater, river flooding, storm water).
• Water can degrade from 1 to 2 to 3 with time and temperature.
• Mold present? The S520 applies; in Texas, so do TDLR's rules at 25 contiguous sq ft.

Official text

This topic is covered in our own words because the standard behind it is copyrighted; we cite it below rather than reproduce it.

Citations

• IICRC S500, ANSI/IICRC S500 Standard for Professional Water Damage Restoration — Definitions, “Category of Water,” pp. 15–16. Best practice
• IICRC S500, ANSI/IICRC S500 Standard for Professional Water Damage Restoration — Sec. 10.4.1–10.4.2, Category of Water; Regulated, Hazardous Materials, and Mold, pp. 44–45. Best practice

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