Categories of water damage

Restoration companies sort water damage into three categories, numbered 1 through 3, based on how contaminated the water is. The category decides what can be dried and saved, and what has to go. It also sets how much protective gear the crew needs.

Category 1: clean water

This is water from a source that started out sanitary, like a supply line, a water heater, or an appliance line. Most of what it soaks can be dried and kept. The catch: drying has to start before the water sits long enough to pick up dirt from what it touches.

Category 2: gray water

Gray water carries some contamination. It could make you sick if you’re exposed to it. Overflow from a washing machine, dishwasher, or AC condensate line that’s been sitting a while typically falls here. Some materials can still be saved. But each call takes more caution than a clean category 1 loss.

Category 3: black water

This is grossly contaminated water, carrying bacteria, waste, or other hazards. Sewage backups and outside floodwater both fall here. Floodwater picks up whatever it crosses on its way in: soil, street runoff, worse. Porous materials it touches, like carpet, drywall, and insulation, usually can’t be saved. They get removed, not dried in place.

Category isn’t fixed: how clean water turns into something else

Water doesn’t stay in its starting category if it sits too long. Leave a category 1 supply-line leak alone for a couple of days and it picks up dirt from carpet, subfloor, and drywall. It shifts toward category 2. That’s another reason speed matters beyond just avoiding mold. The longer any water loss sits, the worse its category gets, never the other way around.

Category vs class: two different measurements

Category and class answer two different questions. Category asks how contaminated the water is. Class asks how much of the home got wet and how deep the moisture goes. The scale runs from class 1 (limited wetness) to class 4 (soaked-through materials like hardwood or plaster). A small category 3 backup and a house-wide category 1 flood need very different responses. And one of them only sounds worse on paper.

Why the category changes the whole job

Category sets the playbook for everything that follows. It decides the gear, what gets dried or tossed, and how the space is treated during cleanup. A category 1 job might mean drying equipment and not much else. A category 3 job means protective gear, careful containment, and a much shorter list of things that get saved.

Where common Katy losses typically land

A burst supply line or a washing machine hose failure usually starts as category 1. An AC condensate overflow that dripped for a while often lands in category 2. So does an appliance leak that sat before anyone noticed. Floodwater from a rising creek or reservoir pool, and any sewage backup, is category 3 from the start. Our flood cleanup and sewage cleanup pages break down what that category 3 reality means in each case.

Knowing the category early helps set expectations, especially on cost. A category 3 job discards more material and needs more gear than a simple category 1 dry-out. Our restoration cost guide breaks down the other factors that drive an estimate up or down.

The category sets the playbook before a single fan turns on. Knowing which water you’re standing in is the first real decision in any water loss, even before the drying starts.