Technical Papers

Assessing Categories and Classes of Water

Friday, June 23rd, 2017 by Chelsea Cannata

In Verona, PA and surrounding areas it is important to know the different classes and categories of water before touching or cleaning out your belongings in the affected area yourself. The affected areas are separated by category because sometimes the water that has damaged the affected area is contaminated and special precautions are necessary.


When talking about the different categories of water it refers to the range of contamination in the water. This can be effected by the source of the water, the time it has sat there, and the temperature. These can produce adverse health effects and can even damage the structure further.


Category 1 water originates from a sanitary water source and does not pose any substantial risks. Some examples of category 1 water are but not limited to supply lines breaking, tub or sink overflow with no contaminants, melting ice or snow, falling rainwater, and sometimes even broken toilet bowls. In the case of the broken toilet bowl, they must not contain any contaminants or additives.


However, there are some exceptions to this rule. If category 1 water flows into an uncontaminated building it does not institute immediate change however if it flows into a contaminated building then it can constitute an immediate change. A common way to tell if category 1 water has changed is by the odor of the water.


Category 2 water contains significant contamination and has the potential to cause discomfort or sickness if contacted or consumed by humans. Category 2 can contain potentially unsafe levels of microorganisms or nutrients for microorganisms. Some examples of category 2 water can include but are not limited to, discharge from washing machines or dishwashers. Overflow from toilet bowls on the room side of the trap with a decent amount of urine but no feces, and lastly a broken waterbed or aquarium.


Category 2 can also deteriorate into category 3 depending on the length of time that they are wet and the temperature of the affected area.


Category 3 water is greatly contaminated and can contain pathogenic, toxigenic, or other harmful agents. Some examples of category 3 water can include but are not limited to, sewage, waste line backflows that originate from beyond any trap regardless of any visible content or color. Also, all forms of flooding from seawater, rivers, streams, and other contaminated water entering or affecting the indoor environment is considered a category 3 water damage.


Category 3 water can carry trace levels of regulated or hazardous materials which is why it is considered category 3 water.


Water is separated into these categories so that the restoration workers can assess a job and then decide what category the water is. Then from there the workers will take the proper precautions to keep themselves and the homeowners safe from hazardous materials.


The classes of water intrusion are separated into four different classes. The classification is based on the approximate amount of wet surface area, and the permeance and porosity of the affected material remaining within the drying environment at the time drying is initiated. The information that determines class is gathered in the inspection process.  


Class 1 water is the least amount of water absorption and evaporation load. It is when 5% or less of the water intrusion meets wet porous materials such as but not limited to carpet, and fiber filled insulation. This in from a combination of the walls, floor, and ceiling surface area.


Class 2 water is water intrusion where wet porous materials mentioned above represent 5-40% of the walls, floor, and ceiling surface area.


Class 3 water intrusion is where wet porous materials mentioned above represent 40% or more of the walls, floors, and ceiling surface area.


Class 4 water intrusion involves a significant amount of water absorption into low evaporation materials such as plaster, wood, concrete, and masonry. Also, low evaporation assemblies such as multilayer subfloors, gym floors, and other complex built up assemblies. When drying a category 4 water intrusion special methods may need to be used. You may also need longer drying times, or substantial water vapor pressure differentials.


Water is separated into these classes so that the restoration workers know whether or not the walls, or ceiling need to be cut out and repaired with new or if they can be dried out and saved. When it comes to the flooring however if a section of the flooring is a higher class then the flooring in that room needs to be replaced. The typical cut off for that is in the doorways of the affected room. 

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