Water Damage
Clean, Grey, and Black Water: Water Damage Categories
Water damage is sorted into three categories by how contaminated the water is. Category 1 is clean water, Category 2 is grey water, and Category 3 is black water, which includes sewage. The category decides what can be dried and kept, what has to be torn out, and how careful everyone needs to be during cleanup.
These categories come from the ANSI/IICRC S500, the industry standard for professional water damage restoration. You do not need to memorize the standard. You just need to know which kind of water you have, because it changes your first steps.
The three categories at a glance
| Category | Common name | Typical sources | What it usually means |
|---|---|---|---|
| 1 | Clean water | Broken supply line, overflowing sink or tub with clean water, leaking water heater | Often dried in place if caught early |
| 2 | Grey water | Washing machine or dishwasher drain water, a toilet overflow with urine but no solid waste | Wear gloves. Soft materials it soaked into may need to go. |
| 3 | Black water | Sewage, a backup from beyond a drain trap, rising water from rivers or streams | Keep people out. Porous materials it touched usually come out. Call a professional. |
The sources in this table are common examples, not a rule. The actual category depends on what is in the water and what it touched.
Category 1: clean water
Category 1 water starts out clean. Think of a burst pipe or a supply line that splits under the kitchen sink. It is the easiest kind to deal with, as long as you move quickly.
If you catch it early, many materials can be dried and kept. The EPA says to dry water-damaged areas and items within 24-48 hours to prevent mold growth. Shut off the water, remove what you can, and start drying the same day.
Category 2: grey water
Grey water has some contamination in it. It is not sewage, but you should not touch it with bare hands or let kids and pets play in it. Washing machine and dishwasher drain water are common examples.
Hard surfaces can usually be cleaned and dried. Carpet pad and other soft materials soaked with grey water often have to be removed. If you are not sure, treat it as the dirtier category.
Category 3: black water
The IICRC S500 defines Category 3 water as "grossly contaminated". It says this water "can contain pathogenic, toxigenic or other harmful agents and can cause significant adverse reactions to humans if contacted or consumed." The standard's examples include sewage, waste line backflows that come from beyond a trap, and rising water from rivers or streams.
In a Cincinnati-area home, Category 3 often means a sewer backup through a basement floor drain or a toilet. It can also mean outside floodwater that came in from the ground.
The EPA is clear about this kind of damage. If water damage was caused by sewage or other contaminated water, it says to call in a professional who has experience cleaning and fixing buildings damaged by contaminated water.
Not all storm water is black water
A roof leak during a storm is not automatically Category 3. In a 2026 position statement, the S500 consensus body said that "top-down water ingress, wind-driven rain and water from weather related events are not automatically considered Category 3 Water". The category depends on whether the water is actually grossly contaminated, which takes an inspection.
So rain coming through a ceiling after a windstorm may be handled as cleaner water. Floodwater rising into a basement from outside is a different story.
Water can get worse over time
A category is not fixed. Clean water can become grey or black water if it sits. The S500 says that "time and temperature can affect or retard the amplification of contaminants, thereby affecting its category."
In plain words, clean water that sits for days in a warm basement, soaking into carpet and dirt, is no longer clean. August heat makes this worse. That is one more reason to start drying fast.
How the category changes the cleanup
The category drives the scope of work. Here is the general pattern:
- Category 1, caught early. Remove water, pull up wet pad, dry walls and floors, and check moisture. Many materials can stay.
- Category 2. More soft material comes out. Surfaces get cleaned before drying.
- Category 3. Soft materials the water touched, such as carpet, pad, the bottom of drywall, and insulation, usually come out. Surfaces get cleaned and treated before drying.
For Category 2 and 3 water, the S500 says that remediation "should occur prior to restorative drying and restorers shall use contamination controls and appropriate worker protection." In other words, clean up the contamination first, then dry.
Who decides the category?
The restoration contractor makes a first call after an inspection. The S500 calls this a "preliminary determination," a process performed by the restorer to set the category for the scope of work.
For higher-risk cases, the standard says an indoor environmental professional should be brought in. Examples include homes with high-risk occupants, a likely risk of health effects, or a need to confirm what the contamination is. If someone in your home is elderly, very young, pregnant, or has a weak immune system, mention that up front.
Staying safe around dirty water
- Keep children and pets out of the area.
- Wear rubber boots, waterproof gloves, and eye protection.
- Do not touch your face while working. Wash your hands well afterward.
- Stay out of standing water near outlets, cords, or the electrical panel.
- Throw away food or drinks that the water touched.
Category is not the same as coverage
Insurance does not pay based on the water category. It pays based on the cause and your policy. A clean-water pipe burst and a sewage backup are treated very differently by most policies, but that is because of the cause.
Sewer and drain backup is usually covered only if you added it to your policy. Our guide to sewer backup insurance in Ohio explains how that works. For water coming in from outside, see flood insurance vs homeowners insurance in Ohio.
How Shamrock can help
Our water damage restoration service covers clean water, grey water, and sewage water removal and restoration. We photograph the damage, write a repair scope, and can meet your adjuster at the house. Call (513) 999-9015 or request a free estimate. The phone line is answered 24 hours a day.
FAQ
Is toilet overflow water black water?
It depends on what is in it. A toilet overflow with urine but no solid waste is often treated as grey water. Overflow with solid waste, or sewage coming up from the drain line, is treated as black water.
Can I clean up grey water myself?
For a small amount on a hard floor, often yes. Wear gloves, clean with detergent, and dry the area fully. If it soaked into carpet, walls, or a large area, get help.
Can carpet be saved after a sewage backup?
Usually not. Carpet and pad hold contamination deep in the fibers. Hard furniture and some hard surfaces can often be cleaned.
Does the water category affect how long cleanup takes?
Yes. Category 2 and 3 jobs need cleaning and removal before drying, so they usually take longer than a clean-water job of the same size.