A categorization of the level of contamination of water in a damaged structure is required to perform loss assessment and evaluation activities.  The category of water contamination must be considered so that procedures can be established for processing water-damaged structures and materials safely.  Water damage is divided into three general categories:  Category 1 – Clean Water;  Category 2 – Gray Water;  Category 3 – Black Water.  The category of water contamination is not determined by the color of the water, rather the category is determined by the source, contents, history and characteristics of the water, as described below.

Category 1 – Clean Water

Category 1 water damage is referred to as “Clean Water.”  Clean water originates from a source that does not pose substantial harm to humans.  Examples of clean water sources may include, but are not necessarily limited to, broken water supply lines, tube or sink overflows with no contaminants, appliance malfunctions involving water supply lines, melting ice or snow, falling rainwater, broken toilet tanks and toilet bowls that do not contain contaminants or additives.

Clean water that has contact with structural surfaces and content materials may deteriorate in cleanliness as it dissolves or mixes with soils and other contaminants, and as time elapses. 

Category 2 – Gray Water

Category 2 water damage is referred to as “Gray Water.”  Gray water contains a significant level of contamination and has the potential to cause discomfort or sickness if consumed by or exposed to humans.  Gray water carries micro-organisms.  Examples of gray water sources may include, but are not necessarily limited to, discharge from dishwashers or washing machines, overflows from toilet bowls with some urine (no feces), sump pump failures, seepage due to hydrostatic pressure, broken aquariums and punctured water beds.  Gray water may contain chemicals, biocontaminants (fungal, bacterial, viral, algae) and other forms of contamination includeing physical hazards.

Time and temperature aggravate category 2 water damage contamination levels significantly.  Gray water in flooded structures that remains untreated for longer then 48  hours may change to category 3 – black water.

Category 3 – Black Water

 Category 3 water damage is referred to as “Black Water.”  Black water contains pathogenic agents and is grossly unsanitary.  Black water includes sewage and other contaminated water sources entering or affecting the indoor environment.  Category 2 water damage that is not removed promptly from the structure may be reclassified as category 3 water damage.  Toilet backflows that originate beyond the toilet trap is considered black water contamination, regardless of visible content or color.

Category 3 water includes all forms of flooding from seawater, ground surface water and rising water from rivers or streams.  Such water sources carry silt and organic matter into structures and create black water damage conditions.

The water is considered to be category 3 water in situations where structural materials and/or contents have been contaminated with such contaminants as pesticides, heavy metals, or toxic organic substances.