Cleaning guide

Clean Water, Gray Water, or Flood Water: The Categories of Water Damage

Updated October 4, 20265 min read

Close-up of a Water Claw extraction tool on carpet in Las Cruces, NM, used when cleaning up water damage

Water damage falls into three categories based on how contaminated the water is. Category 1 starts clean, such as a broken supply line. Category 2 carries some contamination, such as washing machine discharge. Category 3 is grossly contaminated, such as sewage or rising water from a river. The category decides what can be dried and what has to be removed.

In this article

What are the three categories of water damage?

The ANSI/IICRC S500 standard for water damage restoration sorts water into three categories by contamination. Category 1 is water that starts clean, such as a broken supply line or an overflowing sink with no contaminants. Category 2 carries a meaningful level of contamination, such as discharge from a washing machine or dishwasher. Category 3 is grossly contaminated, and the standard lists sewage, waste line backflows from beyond a trap, and rising water from rivers or streams as examples. The category describes the water, not the size of the job. A small sewage backup is still Category 3, and a large supply line flood can still be Category 1.

Is storm flood water always Category 3?

No, not automatically. The S500 consensus body published a position statement on 16 March 2026 stating that top-down water, wind-driven rain, and water from weather events are not automatically considered Category 3. The deciding factor is whether the water is grossly contaminated, and the restorer determines that through an inspection on site. In Las Cruces terms, monsoon rain coming through a roof is judged on what it passed through. Runoff that crossed a yard, a street, or an arroyo before coming under a door is a different case, because it brings soil and debris along. Either way, the category comes from the inspection, not from the word storm.

How does the category change what gets removed?

The higher the category, the more porous material comes out. Porous materials such as carpet pad, drywall, and insulation soak up whatever is in the water and cannot be rinsed clean from the inside. With Category 1 water caught early, carpet and sometimes pad can be extracted and dried in place. With Category 3 water, porous materials that soaked it up are generally removed rather than dried. Hard surfaces such as tile and sealed concrete can usually be cleaned whatever the category. Aggie Carpet and Tile Cleaning makes that call on site with moisture readings, then removes and hauls away what cannot be saved during emergency water extraction.

Can clean water turn into a worse category?

Yes. The S500 standard notes that time and temperature affect the category of water, and that the condition of the water after it touches materials on site matters, not only where it started. A supply line leak that soaks a carpet and sits for days in a warm room can move past the category it started in. The same happens when clean water flows across a dirty floor or picks up debris on its way through a building. That is why the timeline is one of the first questions on a water call. Clean water caught in the first hours gives you the most options.

What should you avoid doing with flood water?

A few common moves make a flood cleanup harder. Do not mix cleaning chemicals on a flooded floor, since some combinations react with each other. Do not run an evaporative cooler in the wet rooms, because it adds moisture to the air that the drying then has to remove. Do not drag runoff-soaked pad through dry rooms, which spreads silt to carpet that was fine. Stay out of standing water near outlets or appliances. If the water came from a sewer or septic backup, treat it as a separate job, and see sewage and bodily fluid cleanup for how that is handled.

Related services

Related cleaning services

The water source decides the cleanup. Aggie Carpet and Tile Cleaning provides emergency water extraction, water damage restoration, and sewage cleanup for Las Cruces homes and businesses.

Emergency Water Extraction Sewage and Bodily Fluid Cleanup Water Damage Restoration

Questions

Common questions about this topic

What is Category 3 water?

Category 3 water is grossly contaminated water under the ANSI/IICRC S500 standard. Examples include sewage, waste line backflows from beyond a trap, and rising water from rivers or streams. Porous materials soaked by Category 3 water, such as carpet pad and drywall, are generally removed rather than dried in place.

What is the difference between gray water and black water?

Gray water is the common name for Category 2, water with some contamination, such as washing machine or dishwasher discharge. Black water is the common name for Category 3, grossly contaminated water such as sewage. The difference changes how much material has to be removed during cleanup.

Is a roof leak Category 1 water?

Not necessarily. Rain coming through a roof is judged on what it passed through on the way in, such as roofing material, insulation, and ceiling debris. An inspection decides the category. The IICRC stated in March 2026 that weather-related water is not automatically Category 3, which also means it is not automatically clean.

Who decides the category of water on a job?

Under the S500 standard, the restorer makes a preliminary determination of the category after inspecting the site and gathering information about the source and timeline. When elevated risk factors are present, the standard recommends bringing in an indoor environmental professional to assess contamination levels.

Does Aggie handle all three categories of water?

Aggie handles water extraction and cleanup for supply line leaks, storm water, and runoff, including mud and silt, in homes and businesses. Sewage and septic backups are handled under the separate sewage and bodily fluid cleanup service. Active mold is referred to a certified remediation specialist.

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