There are 3 primary types of categories of water damage when a house floods. A water category is determined by the water source. Insurance adjusters and water damage technicians often use the water category when deciding whether to dry or remove materials in a home. A water category can also determine any safety measures that need to be taken during the dry out. There are 3 categories of water: white, grey, and black.
According to Wikipedia:
Category 1 Water – Refers to a source of water that does not pose substantial threat to humans and classified as “Clean Water”. Examples are broken water supply lines, tub or sink overflows or appliance malfunctions that involves water supply lines.
Category 2 Water – Refers to a source of water that contains a significant degree of chemical, biological or physical contaminants and causes discomfort or sickness when exposed or even consumed. Known as “Grey Water”. This type carries micro organisms and nutrients of micro organisms. Examples are toilet bowls with urine (no feces), sump pump failures, seepage due to hydrostatic failure and water discharge from dishwashers or washing machines.
Category 3 Water – Known as “Black Water” and are grossly unsanitary. This water contains unsanitary agents, harmful bacteria and fungi, causing severe discomfort or sickness. Type 3 category are contaminated water sources that affects the indoor environment. This category includes water sources from sewage, seawater, rising water from rivers or streams, ground surface water or standing water. Category 2 Water or Grey Water that is not promptly removed from the structure and or have remained stagnant for 48-72 hours may be re classified as Category 3 Water. Toilet back flows that originates from beyond the toilet trap is considered black water contamination regardless of visible content or color.
When dealing with contaminated water, a professional water damage mitigation company will take certain precautions such as using gloves, masks and possibly even Tyvek suits. It is important to remove any small children or animals from the area affected when the water is not clean.