TL;DR
Category 1 is clean water from a supply line, Category 2 is gray water carrying some contamination, and Category 3 is grossly contaminated water including sewage, groundwater, and outdoor flooding. Category 3 carpet and pad are removed, never cleaned. Category 2 usually means the pad comes out even when the carpet is saved. Category degrades over time -- clean water does not stay clean.
Why Categories Exist
Restoration decisions are not made by looking at how wet something is. They are made by asking what was in the water and how long it has been there.
The category system gives that first question a standard answer, so a technician, an adjuster, and a homeowner are describing the same thing. It drives what gets dried, what gets cleaned, what gets removed, and what protective equipment the crew wears.
Category is about contamination. A separate scale, called class, describes how much water and how much material absorbed it. The two together set the drying plan.
Source: IICRC S500 standard for professional water damage restoration
Category 1: Clean Water
Water from a sanitary source that poses no substantial risk at the moment it arrives.
Typical sources are a broken supply line, a leaking water heater tank, a supply-side toilet leak from the tank or the fill line, a melting ice maker line, rainwater entering without contacting contaminated material, and a burst pipe carrying potable water.
On Category 1 caught quickly, drying in place is often possible. Carpet and pad can frequently both be saved if extraction starts immediately and the drying plan is sound.
The catch is that Category 1 does not stay Category 1. Water sitting in carpet picks up soil, feeds organisms, and degrades. Restoration standards treat category as a condition that can worsen with time, temperature, and what the water touches on the way.
What Is Category 2 Water?
Category 2 is gray water: water with significant contamination that could cause discomfort or illness if contacted or consumed. Typical sources are washing machine and dishwasher discharge, an overflowing sink or tub with soap and body soil, a toilet overflow from the tank side with urine but no solids, and aquarium water. The pad usually comes out even when the carpet is saved.
Category 2 in Practice
The reason the pad comes out is that it cannot be reliably cleaned in place. Pad is absorbent, porous, and sits against the subfloor where nothing can rinse it. Verifying that a contaminated pad is clean is not possible.
Carpet is different. It can be pulled up, cleaned, sanitized, dried, and reinstalled over new pad, because both sides are accessible. Whether that is worth doing depends on the carpet's age and condition and on how long it sat wet.
Category 2 degrades to Category 3 with time. Gray water on carpet covers what happens to the pad and the backing in more detail.
Category 3: Black Water
Grossly contaminated water containing pathogens, toxins, or other harmful agents.
Sources include sewage of any kind, a toilet overflow from the bowl side, water from beyond a toilet trap, rising groundwater, flooding from rivers, streams, or storm surge, water that has passed through contaminated ground or building materials, and any Category 1 or 2 water that has sat long enough to degrade.
Category 3 carpet and pad are removed and disposed of. They are not cleaned. This is the firmest rule in the entire category system, and it is not a matter of how good the cleaning company is. Porous materials that have absorbed grossly contaminated water cannot be verified clean.
That includes the pad, the carpet, and often the drywall bottom edge, insulation, and any other porous material in the affected area. A toilet overflow is one of the most common residential Category 3 events -- see toilet overflow on carpet for how supply side and bowl side differ.
Time Moves Everything Downward
Category and time are not independent.
Clean water sitting for two days is no longer clean water. Gray water sitting for a week is functionally black water. That is why the 24 to 48 hour wet carpet window matters so much: it is the boundary where a Category 1 loss with a good outcome turns into a removal job.
A technician establishing scope will ask what the source was and when the water arrived. Both answers change the plan.
What This Means for Your Floor
Here is the short version of how the categories usually land.
Category 1, caught fast. Carpet and pad both often stay. Extraction, air movers, dehumidification, and daily monitoring.
Category 1, past the window. Pad out. Carpet evaluated.
Category 2. Pad out. Carpet possibly saved with removal, cleaning, sanitizing, and drying.
Category 3. Carpet and pad both out. Remediation and disinfection of what remains.
How a drying tech decides to save carpet walks the full decision, and when the pad comes out but the carpet stays covers the most common middle outcome.
Do Not Guess the Category Yourself
If the source is obvious and clean, and you caught it within minutes, you are probably right. Beyond that, the category should be established by someone who can trace where the water traveled and what it touched.
Water that started clean at the water heater and then ran across a garage floor and under a wall is not clean anymore. That is exactly the kind of judgment the category system exists to standardize.
FAQ
What are the three water damage categories?
Category 1 is clean water from a sanitary source such as a supply line. Category 2 is gray water with significant contamination, such as washing machine or dishwasher discharge. Category 3 is grossly contaminated water including sewage, groundwater, and outdoor flooding.
Can Category 3 carpet be cleaned instead of replaced?
No. Carpet and pad exposed to Category 3 water are removed and disposed of. Porous materials that absorbed grossly contaminated water cannot be verified clean, so cleaning is not an accepted option regardless of the equipment or chemistry available.
Does clean water stay Category 1?
No. Category degrades with time, temperature, and what the water contacts. Clean water sitting in carpet picks up soil and supports microbial growth, so a Category 1 loss left for days is treated as a higher category when a crew arrives.
Is a washing machine overflow Category 2 or Category 3?
Discharge water carrying detergent and body soil is generally treated as Category 2. It moves toward Category 3 if it has sat for an extended period, or if the overflow involved a drain line backing up rather than the machine simply discharging.
Who decides what category my water damage is?
A qualified restoration technician, based on the source, the path the water traveled, what it contacted, and how long it has been present. It matters because the category determines whether materials are dried, cleaned, or removed, so it is not a judgment to make casually.
Does the category affect whether mold remediation is needed?
Indirectly. Category describes contamination at the source; mold growth is about moisture and time. Any category left wet long enough can produce growth, and visible growth moves the job into mold remediation, which is a separate trade with its own containment and clearance requirements.
For a whole-room reset rather than a single treatment, see carpet cleaning services.
Category is the first question a crew asks and the one that decides most of what follows, which is why the source of the water matters more than the size of the puddle. Every home is different, so the real number depends on size, condition, and what you want covered. Get a quote and we will walk you through it.