Category is about contamination potential
Water that begins relatively clean can deteriorate after contacting soils, contaminants, building materials or microbial reservoirs. Source history and exposure pathway matter.
Color and odor alone cannot reliably classify water.
Category 2 conditions
Category 2 commonly describes water containing significant contamination that could cause discomfort or illness if contacted or consumed.
Examples depend on the actual source and circumstances; the important field question is what contaminants may be present and which materials can be effectively cleaned.
Category 3 conditions
Category 3 describes grossly contaminated water that may contain pathogenic, toxigenic or otherwise harmful agents. Sewage and many forms of floodwater or groundwater can fall into this higher-risk condition.
Drying strategy must be integrated with contamination control, removal decisions, containment and worker/occupant protection.
Why category can change
Time, temperature, contact with contaminated materials and stagnation can worsen conditions. A project should not assume the initial source classification remains valid after prolonged migration.
Uncertain water should be treated as uncertain until qualified evaluation resolves the exposure conditions.
Use this guide with field evidence
This guide explains the decision factors specific to category 2 vs. category 3 water damage. A site-specific conclusion still depends on the actual assembly, source condition, access, measurements and changes observed during the project.
For category 2 vs. category 3 water damage, use this page as the focused reference. Return to Structural Drying Intelligence to place it inside the larger drying decision sequence.