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Categories and classes of water damage

The IICRC (Institute of International Cleaning and Restoration Certification) is an American National Standards Institute (ANSI) standards developer. They produce standards for the cleaning and restoration Industry. The current standard that addresses water damage restoration is the S500 Standard and Reference Guide for Professional Water Damage Restoration (S500).

In the S500, water is described relative to its degree of contamination in 3 categories. The determination of the category helps restorers to determine the restorability of an affected material and to determine the need for personal protective equipment to be worn by restorers during restoration.

Category 1
Category 1 water originates from a sanitary (clean) water source and does not pose substantial risk from dermal, ingestion, or inhalation exposure.  (i.e., broken water supply lines; tub 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).

Category 2
Category 2 water contains significant contamination and has the potential to cause discomfort or sickness if contacted or consumed by humans.  Category 2 water can contain potentially unsafe levels of microorganisms or nutrients for microorganisms, as well as other organic or inorganic matter (chemical or biological).  (i.e., discharge from dishwashers or washing machines; overflows from washing machines; overflows from toilet bowls on the room side of the trap with some urine but no feces; seepage due to hydrostatic pressure; broken aquariums and punctured water beds).

Category 3
Category 3 water is grossly contaminated and can contain pathogenic, toxigenic or other harmful agents.  (i.e., sewage; toilet backflows that originate from beyond the toilet trap regardless of visible content or color; all forms of flooding from seawater; rising water from rivers or streams; and water entering or affecting the indoor environment, such as wind-driven rain from hurricanes, tropical storms, or other weather-related events that can carry contaminants (e.g., silt, organic matter, pesticides, heavy metals, regulated materials, or toxic organic substances).

Category 1 or 2 water can deteriorate to 2 or 3 respectively.  Category 1 water that flows into an uncontaminated building does not constitute an immediate change in the category. However, Category 1 water that flows into a contaminated building can constitute an immediate change in the category. Once microbial organisms become wet from the water intrusion, depending upon the length of time that they remain wet and the temperature, they can begin to grow in numbers and can change the category of the water. Odors can indicate that Category 1 water has deteriorated.

In the S500, water intrusion is also separated out into 4 classes. Each class identifies the relative amount of water left in a material after initial extraction, which needs to be evaporated in order to dry. The class of water intrusion helps restorers to determine the initial amount of dehumidification needed to dry a building.

Class 1
In a Class 1 water intrusion, there is a minimal amount of water that has flowed into the area and the materials are predominately low porosity.  This results in there little moisture remaining after the bulk water was removed and therefore a minimal amount of evaporation is needed to complete the drying.

Class 2
In a Class 2 water intrusion, there is a significant amount of water that has flowed into the area and wet materials are medium to high porosity (e.g. carpet, gypsum wall board). The result is a greater absorption into materials, and that after the bulk water was removed there is a greater amount of water to evaporate to complete the drying.  The scope of what is wet generally is confined to what got wet as a result of what flowed across a floor with some adsorption into other materials.

Class 3
A Class 3 water intrusion represents the greatest amount of absorption into materials, resulting in the highest potential rate of evaporation needed after the bulk water is removed.  It also includes a major part of all structural surfaces within the affected area  (e.g. carpet, gypsum wall and ceiling board).

Class 4 
A Class 4 water intrusion results in the majority of the moisture being, trapped or bound within building materials and assemblies, resulting in a low potential rate of evaporation after bulk water removal.  Affected materials are typically low in porosity (e.g. plaster, hardwood, concrete, masonry) or the building assemblies (e.g. gym floors, structural cavities) may require special methods, longer drying times, or substantial vapor pressure differentials.

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