Extreme water loss situations are often tragic events that have the potential to destroy homes and wreck lives. Though they aren’t always preventable, it can help to know how catastrophic water occurrences are classified, and what to expect if you ever find yourself in the midst of one. 

Significant water loss events are referred to as Category 3, Class 3 or Class 4 water losses, though these terms are not interchangeable. Each qualifying water situation is classified on an individual basis and is determined in relation to the materials affected, the severity to which they are affected and the type of water that has invaded the premises. 

Category 3 Water Losses

How They Are Determined

Category 3 water losses are defined by the source of the water affecting the structure, and the potential contaminants therein. If it is suspected that the water that has entered a structure has pathogenic qualities, has originated from an unsanitary source, or is ground surface water that is traveling horizontally from outside, the water event in question will be rendered a Category 3 water loss. 

Though Category 3 water may tend to have a distinct look or smell about it, the appearance and odor of the water are not surefire ways to determine whether or not it contains contaminants. In fact, there are times when Category 3 water is clear, and may look “clean” by many standards. For this reason, the term “black water”, as Category 3 water were formerly named, is not completely accurate. 


Water events classified as Category 3 often come from unsanitary sources, such as sewage backup. In addition, any water that enters a building or structure horizontally from ground surfaces are also considered Category 3, as they have the potential to carry pathogens and other contaminants. 

Potential Health Hazards

Coming in direct contact with wastewater or groundwater can be dangerous, and even fatal. Common bacteria and pathogens found in these types of waters include E. coli, salmonella and cholera, just to name a few.

If the client finds him or herself in a situation involving Category 3 water, he or she should never attempt to handle the situation without the help of a water remediation expert.

Having said that, it may sometimes be necessary to shut off the source of the contaminated water, if at all possible. When this is the case, it is crucial that the person attempting the task wear appropriate protective gear, such as boots, glasses and gloves. 

If the water source cannot be shut off safely, owners and occupants should vacate the premises and leave the job to a restoration professional.

In addition, owners and occupants should take special care to remove any high-risk individuals from Category 3 water situations immediately. This includes children, pregnant women, those with immunodeficiency disorders, the elderly and anyone else who may be at a physical disadvantage. 

Bear in mind that if water has come into contact with electrical sources, No one should attempt to impede the water source. Owners and occupants should move themselves and others to safety, and contact a remediation professional, without delay.


When the remediation team arrives, they will likely come dressed in appropriate PPE, or personal protective equipment. After touching base with the client, the remediation staff will attempt to take control of the situation by locating and shutting off the source, only if they are able, and if the owners or occupants have not successfully done so, already.

As for the aftermath of a Category 3 water event, adhering to proper protocol is paramount. Owners and occupants of the affected structure can expect any soaked carpet, fabrics and other porous materials to be thrown out. Non-porous structures and surfaces will be thoroughly cleaned. 

After unsalvageable items and materials have been removed, the drying process can begin. Technicians will use a wide range of drying equipment based on the needs of the affected home or establishment including dehumidifiers, air movers and more.

Special Circumstances

There are times when some items that are deemed valuable, such as oriental rugs, may be spared. When this is the case, the valuables must be deeply cleaned and chemically treated to help control the growth of microbes. Moreover, a third party inspection will likely be necessary to ensure the safety of the items spared.

It is important to note that feelings of anxiety, stress and anger are common at the spur of a water event. It can be understandably difficult to see valuables destroyed, and ultimately, discarded. Nevertheless, it is the job of the restorer to follow proper protocol for the protection and safety of all parties involved.

If a client decides to stand in the way of safety regulations, the restorative technician reserves the right to leave the job uncompleted. Safety is crucial following a Category 3 water event. Thus, remediation teams must follow proper guidelines to ensure the well-being of everyone involved. 

Class 3 and Class 4 Water Intrusions

How They Are Determined

Not to be confused with a Category 3 water event, Class 3 and Class 4 water intrusions can do serious damage to a structure or property. While a Class 3 or 4 water event can also be categorized as a Category 3 water loss, they are not the same. 

Category 3 water losses refer to water that is heavily contaminated or has come from a ground surface source, whereas Class 3 and Class 4 water events refer to the amount and type of materials that are affected within a specified waterlogged structure. 

For example, a Class 3 water intrusion is indicated as having more than 40% of the combined ceiling, flooring and wall components affected by water. In this scenario, low-porosity materials such as wood and concrete haven’t absorbed much moisture. 

In many Class 3 cases, moisture may be observed wicking up the wall at more than two feet, while drywall, and even the insulation within the walls, may have become affected. 

Class 4 water intrusions, on the other hand, often require specialized drying equipment as low-evaporation materials, including hardwood floors, concrete and plaster, have been deeply saturated. In these events, it takes time, careful monitoring and ever-changing techniques to effectively dry the area affected. 

It is important to note that either event, though catastrophic in nature, can involve Category 3 water, but not always. Clients should allow their technician to make determinations as he or she sees fit, given the circumstance. 


A Class 3 water intrusion can have varying causes, but oftentimes, it is caused by water that has entered a building or structure from overhead. This can be the result of roof damage or severe winds that have enabled rainwater to make its way inside, or pipelines that have burst and have filled rooms and floor spaces with a multitude of water. 

A Class 4 water intrusion is more about the type of materials affected, and can be caused by a variety of situations. In the end, these are the hardest types of intrusion cases to dry, as the materials affected often have low evaporation rates.

Potential Health Hazards

Health hazards related to Class 3 and 4 situations depend largely on the type of water that has invaded the area. 

Having said that, Class 3 water events, unless quickly handled, can rapidly escalate out of control, as water penetrates hard to reach places, such as behind drywall or within insulation material. This lends itself to the potential for mold growth and other microbial activity if it isn’t addressed right away using effectual techniques. 

Likewise, Class 4 water events often lead to the buckling, crowning or cupping of hardwood, which can make for unlevel surfaces. Tripping, slipping, falling and other physical injury risks are thereby increased. 

No matter the situation, when dealing with any sort of water event, the same rules of safety apply. Owners and occupants should always wear the appropriate safety gear mentioned earlier if attempting to shut off water sources, and should never enter water that has come in contact with electrical functions and appliances.


Remediation measures for a Class 3 water event depend on the structures affected. However, it can involve the drilling of holes in the wall to allow for maximum airflow and the disposal of any insulation that has become wet. Any sagging ceiling surfaces will be promptly removed and replaced, and appropriate drying techniques fit for the situation will be utilized.

The flooring may or may not be replaced, depending on the materials affected and the category of water that has occupied the area. 

For Class 4 water events, remediation will involve creative measures that will likely change throughout the process to ensure drying effectiveness. The client may notice technicians using both invasive and non-invasive moisture monitoring techniques to keep track of progress. 

The overall drying process of a Class 4 water intrusion may involve the use of dehumidifiers, extraction equipment and more, but the methods used will vary depending on the need and the severity of the situation.


Though many water losses that occur may have been out of the control of the owner of the property, there are a few ways that owners and occupants of homes and businesses can help minimize the chances of a major water event happening.

Owners and occupants should seek to regularly maintain appliances and address any plumbing mishaps, without delay. The longer they wait to address plumbing issues, the more damage may ensue. Over time, pipes may burst, a dishwasher may break or another issue may occur that can subject a structure to irrevocable damage that may cost hundreds, or thousands, of dollars to fix.

There Is Hope for Restoration

For people whose property has been touched by a severe water damage event, the experience can be stifling. Nevertheless, by using well-established methods and the right tools, a water remediation specialist can restore a property back to a safe and healthy environment.