Category 1, 2 and 3 Water Damage Explained
Short answer: Water damage is grouped into three categories by contamination. Category 1 is clean water, such as a broken supply line. Category 2 is gray water with some contamination, such as washing machine discharge. Category 3 is black water, grossly contaminated water like sewage or rising floodwater. The category decides what can be dried and what must be thrown out.
When a restoration crew arrives, one of the first things they decide is what kind of water they're dealing with. That decision drives everything else. It sets the gear, what gets removed, how surfaces are cleaned and often how the claim is handled. If you're facing sewage or floodwater now, Reestorian can connect you with a local provider for sewage backup cleanup in Littleton.
This is general information. Restorers determine the category on site.
What are the categories of water damage?
The categories come from the ANSI/IICRC S500 Standard for Professional Water Damage Restoration, the main rulebook for the trade.
| Category | Also called | Common sources | What it means for cleanup |
|---|---|---|---|
| Category 1 | Clean water | Broken supply line, overflowing sink with no contaminants, water heater, ice maker line | Many materials can be dried in place if work starts quickly |
| Category 2 | Gray water | Washing machine or dishwasher discharge, toilet overflow with urine, aquarium water | Needs cleaning and sanitizing; more materials removed |
| Category 3 | Black water | Sewage, toilet overflow with feces, rising river or stream water, outside floodwater | Porous materials usually removed; full disinfection; protective gear |
What is Category 3 water?
The S500 standard defines Category 3 water as grossly contaminated. It can hold germs, toxins or other harmful agents. Its examples include sewage, seawater flooding and rising water from rivers or streams. Under the standard, Category 2 and 3 water require contamination controls, protective equipment and remediation before restorative drying.
Sewage or floodwater in the house? Call to reach a local cleanup provider.
Call (928) 394-5135How water changes category
Water doesn't stay in one category. Clean water gets worse as it:
- Sits. Water left for days starts to grow bacteria and mold.
- Travels through materials. Water that runs through insulation, under flooring or across a dirty basement floor collects contaminants.
- Mixes with other sources. A clean-water leak that reaches a floor drain or soil can become gray or black water.
- Gets warm. Warm, still water supports faster microbial growth.
That's why a clean leak left over a long weekend may be treated as gray or even black water by cleanup time.
Is weather-related water always Category 3?
No. In a 2026 position statement, the IICRC says top-down water entry, wind-driven rain and other weather-related water aren't automatically Category 3. The word "can" in the standard's Category 3 examples describes a possibility, not a requirement. The restorer decides the category through inspection and may bring in an indoor environmental professional to assess contamination. Rising floodwater from rivers and streams, however, is listed as an example of Category 3 water.
Water classes: how much is wet
Category describes how dirty the water is. Class describes how much material is wet and how hard it will be to dry.
| Class | What it usually means |
|---|---|
| Class 1 | A small area with little water absorbed |
| Class 2 | A whole room, with carpet and the lower walls absorbing water |
| Class 3 | Water from above soaked ceilings, walls, insulation and floors |
| Class 4 | Materials that hold water tightly, such as hardwood, plaster and concrete |
A basement sewer backup might be Category 3 and Class 2 or 4: dirty water, on a slab that dries slowly.
What gets thrown out after Category 3 water
Colorado public health guidance for sewer backups lists items to discard:
- Mattresses, pillows and foam rubber items
- Upholstered couches and chairs
- Books and most paper products
- Potentially contaminated food and cosmetics
- Stuffed animals and baby toys
- Large rugs, foam-backed rugs and wall-to-wall carpet, with the pad usually replaced even if the carpet can be cleaned
- Anything that can't be thoroughly steam cleaned or disinfected
The CDC adds drywall and insulation contaminated with sewage or floodwater to the list.
Safety by category
| Category | Basic protection |
|---|---|
| Category 1 | Normal care; watch for electrical hazards and slippery floors |
| Category 2 | Gloves and eye protection; wash hands; keep children and pets away |
| Category 3 | Rubber boots, rubber gloves, goggles and washable clothing; respirators on larger jobs; keep vulnerable people out |
The CDC warns never to mix bleach with ammonia or other cleaners. Never switch power on or off while standing in water.
Cleaning and disinfecting after gray or black water
For hard surfaces after a sewer backup, Colorado public health guidance recommends:
- Removing standing water and debris
- Washing surfaces with soap and water
- Disinfecting with 1/4 cup of chlorine bleach per gallon of water, left on for at least a minute
- Rinsing, then washing again with mild soap and water
- Keeping fresh air moving with open windows and fans
Then the area needs to be dried completely. The EPA says mold usually won't grow if wet materials are dried within 24 to 48 hours.
How do restorers decide the category?
The IICRC position statement says the restorer makes the call through an inspection and a preliminary determination. In practice, a provider looks at:
- The source, such as a supply line, an appliance drain, a toilet or the sewer
- What the water touched on its way, like soil, insulation or a dirty floor
- How long it sat before cleanup started
- Smell and appearance, including odor, color and debris
- Who lives there, since infants, older adults and people with weakened immune systems change the level of caution
When it's unclear how dirty the water is, the IICRC notes the restorer may need an indoor environmental professional to test it.
Water category examples in Littleton homes
| Situation | Likely starting category | Why it might change |
|---|---|---|
| Frozen supply line splits in a garage wall | Category 1 | Can degrade if it sits or runs across a dirty floor |
| Water heater tank fails in the basement | Category 1 | Mixes with dust and debris on the slab |
| Washing machine hose bursts | Category 2 | Contains detergent and soil |
| Dishwasher leaks under the cabinets | Category 2 | Food residue and time under cabinets |
| Toilet overflows on an upper floor | Category 2 or 3 | Depends on whether waste was present |
| Floor drain backs up with sewage | Category 3 | Sewage is grossly contaminated |
| Storm runoff flows through a window well | Often treated as Category 3 | Collects soil, fertilizer and debris outside |
Questions to ask your restoration provider
- What category did you assign, and what did you base it on?
- Did the category change since the leak started?
- Which materials will you remove because of the category?
- What protective steps are you taking for my family and pets?
- Will you document the category in the report for my insurer?
Why the category matters for insurance
Category affects the scope, and the scope affects the claim. Category 3 jobs remove more material and take more labor, so they cost more. The cause also matters for coverage. A clean-water pipe burst is often covered by a standard policy. A sewer backup usually needs a water backup endorsement, and outside floodwater needs flood insurance. See sewer backup insurance.
Local note: Contaminated water calls are common in a few kinds of places. In Englewood, older sewer laterals lead to backups. In Lakewood and Castle Rock, creek and runoff flooding can bring outside water into homes. In Lone Tree, a toilet overflow in one condo can reach the unit below.
Related reading: Read what sewer backup insurance covers, and follow the basement flood checklist if the water is in your lower level.
When should you call a water damage professional?
Call a professional when:
- The water is gray or black, or you aren't sure
- Sewage or outside floodwater touched carpet, drywall or furniture
- Clean water sat for more than a day or two
- Anyone in the home is very young, elderly, pregnant or has a weakened immune system
Contaminated water in Littleton? Call (928) 394-5135 to reach a local sewage and water damage cleanup provider.
Frequently asked questions
Is rainwater Category 3?
Not automatically. The IICRC's 2026 position statement says weather-related water, including wind-driven rain, isn't automatically Category 3. The restorer decides based on inspection and how contaminated the water actually is.
Is fire sprinkler water Category 3?
Not by default. Sprinkler water often starts as clean or gray water, but it can collect contamination from stagnant water in the lines, debris and the materials it soaks. The restorer judges the category on site.
Is sump pump water Category 3?
It depends. Groundwater from a sump pit is often treated as gray water, but water that sat, mixed with soil and debris, or came from outside flooding can be Category 3. Ask the provider how they classified it and why.
Can Category 3 water damage be dried in place?
Usually not for porous materials. Carpet, pad, drywall and insulation soaked by Category 3 water are normally removed and discarded. Hard, non-porous surfaces can be cleaned, disinfected and dried.
Do I need protective gear for Category 3 cleanup?
Yes. The CDC recommends rubber boots, rubber gloves and goggles when sewage may be involved, and Colorado public health guidance adds washable or disposable clothing. Larger jobs need respirators and professional equipment.
Sources
- IICRC: Category of Water Damage and Weather-related Events position statement (2026)
- IICRC: ANSI/IICRC S500 Standard for Professional Water Damage Restoration
- CDC: Guidelines for Cleaning Safely After a Disaster
- Colorado Department of Public Health and Environment: Cleaning up after a sewer backup (via Boulder County)
- EPA: A Brief Guide to Mold, Moisture and Your Home
Related guides
Sewer Backup Insurance: What's Covered and What Isn't
Why standard policies exclude sewer backups, what a water backup endorsement covers and who is responsible for the line in Littleton.
What to Do If Your Basement Floods: A Step-by-Step Guide
Ten steps for a flooded basement, from safety and the power panel to drying, insurance and stopping it from happening again.
Dealing with contaminated water?
Call to reach a local sewage and water damage cleanup provider in Littleton.