How we made this guide: picks, prices and specs come from our catalog and the makers' published specs, owner quotes come from customer reviews on our product pages and every guide is checked and edited by Trevor Hall.
Category 3 water damage is grossly contaminated water, such as sewage or rising flood water. The category tells you how dirty the water is. The class (1 to 4) tells you how much water there is and how hard it will be to dry, and the two are independent. A small Class 1 spill can be Category 3, and a Class 4 soak can be Category 1.
For the drying itself, the class drives the equipment. A restoration LGR dehumidifier such as the XPOWER XD-130Li at $3,079 and low-profile air movers such as the XL-760AM at $356 are the core of a Class 2 or Class 3 drying setup, in numbers sized to the room. The category drives what comes out of the building and what workers wear. This post puts both in one table.
Quick answer
Category = how contaminated the water is (1, 2 or 3). Class = how much water and how hard it is to evaporate (1 to 4). Under S500, Category 2 and Category 3 losses both get cleanup with contamination controls and worker protection before drying. For Category 3 the soaked porous materials such as carpet cushion usually come out instead of being dried in place. The drying plan that follows still depends on the class. See our restoration dehumidifiers for the drying side.
A note on sources. The definitions quoted here are from ANSI/IICRC S500, 5th edition (2021), the current edition, as cited in the S500 Consensus Body's February 2026 position statement. The standard is a paid document, so we quote only short definitions. Check your own copy before you write them into a scope of work. The machine facts come from the makers' spec sheets and manuals.
The categories and classes in one table
Most pages on this topic explain categories in one place and classes in another. On a real job you need both at once, because a Category 3 loss that reaches only one wall behaves differently from one that floods a whole floor. This table crosses them. The text in each cell is a plain-language summary of how the work changes, not a quote from the standard.
| Class (amount and difficulty) | Category 1 (clean source) | Category 2 (contaminated, short of Category 3) | Category 3 (grossly contaminated) |
|---|---|---|---|
| Class 1: least wet porous material | Dry in place. Air movers on the wet area and a dehumidifier sized to the room. | Contamination controls and PPE. Clean first, remove wet porous finishes such as cushion, then dry. | Remove affected porous materials. Clean and dry what stays, with protective equipment for the crew. |
| Class 2: more wet porous material | Extract, then dry carpet and cushion in place with air movers and an LGR dehumidifier. | Contamination controls and PPE. Extract, pull the cushion, clean or replace the carpet, then dry. | Carpet and cushion usually come out. Dry the structure behind them. |
| Class 3: most wet porous material | Open walls where needed, extract, then run several air movers and one or more LGR units. | Contamination controls and PPE. Remove wet insulation and other porous material, clean, then run several air movers and one or more LGR units. | Removal first. Dry the framing and slab with a full air mover and dehumidifier setup after the cleanup. |
| Class 4: water bound in dense materials | Specialty drying: low grain dehumidification and slow, steady airflow. A desiccant unit often helps. | Contamination controls and PPE. Clean first, then low grain drying of the dense materials, often with a desiccant unit. | Cleanup and removal first, then specialty drying of what remains. |
What the three categories mean
ANSI/IICRC S500, the Standard for Professional Water Damage Restoration (5th edition, 2021), sorts water by contamination. It looks at where the water came from and what it picked up on the way, not at how it looks.
- Category 3 water is "grossly contaminated and can contain pathogenic, toxigenic, or other harmful agents and can cause significant adverse reactions to humans if contacted or consumed." Its listed examples include "sewage; wasteline backflows that originate from beyond any trap regardless of visible content or color; all forms of flooding from seawater; rising water from rivers or streams".
- Category 1 is the one category where, in S500 section 10.6.7's words, "the restorer can proceed without contamination controls (e.g., erecting containment barriers, establishing pressure differentials)."
- Category 2 is contaminated water short of Category 3. S500 groups it with Category 3 for the work: "With regard to Category 2 or 3 water intrusions, remediation should occur prior to restorative drying and restorers shall use contamination controls and appropriate worker protection."
S500 section 12.2.6 says the categories "refer to the range of contamination in water, considering both its originating source and its quality after it contacts materials present on the job site", and that "Time and temperature can affect or retard the amplification of contaminants, thereby affecting its category." So water can move to a higher category as it sits. The category follows the source and what the water touched, not its color, which leads to the question most homeowners ask first.
Can Category 3 water look clear?
Yes. S500 lists "wasteline backflows that originate from beyond any trap regardless of visible content or color" among its Category 3 examples, so a floor drain backup that looks clear is still Category 3. If you cannot trace the source, treat it as the higher category until a restorer makes the preliminary determination S500 calls for, with an indoor environmental professional brought in when the contamination itself has to be confirmed.
Is storm or rainwater always Category 3?
No. In a February 10, 2026 position statement the ANSI/IICRC S500 Consensus Body wrote: "Top-down water ingress, wind-driven rain and water from weather related events are not automatically considered Category 3 Water." Wind-driven rain is one of the Category 3 examples only when the water is grossly contaminated. The restorer decides that in the preliminary determination after inspecting. Rising water from rivers or streams and all flooding from seawater are listed Category 3 examples. Standing water in a basement with an unknown source is a job for a trained restorer to class.
What the four classes mean
The class describes the size of the evaporation problem. S500 sets the class by the evaporation load, from Class 1 (least) to Class 3 (greatest), with Class 4 for water held deep in dense materials such as plaster, wood, concrete and masonry. Those dense materials release moisture slowly, so ordinary airflow is not enough.
For the sewage cleanup side of Category 3, the sewage cleanup steps post goes through the order of work.
What changes when the water is Category 3
S500 section 10.6.7 says "With regard to Category 2 or 3 water intrusions, remediation should occur prior to restorative drying and restorers shall use contamination controls and appropriate worker protection." For a Category 3 loss that works out to these steps.
- Stop the source and keep people out of the affected area.
- Put on protective equipment suited to the contamination before anyone handles the material.
- Remove standing water. A flood pumper with a continuous pump-out suits a large pool.
- Remove porous materials that the water soaked, such as carpet cushion, and bag them for disposal as local rules require.
- Clean the structure that stays, then dry it with air movers and dehumidifiers.
- Verify the result with a moisture meter before anything is closed up. Our moisture meter readings chart lists normal levels.
The drying in step 5 is the same physics as for any other water loss. The drying plan follows the class, which is why the same LGR and air mover setup shows up in every row of the table above.
The machines for each stage
Four machines from our range cover the stages above: pulling standing water, the main dehumidifier, the airflow and Class 4 drying. The figures are the makers' ratings from their spec sheets and manuals.
Step 3: pulling out standing water
Standing water
Sandia Sniper 24-Gallon 2-Stage Flood Pumper - 80-6001
$2,892
A 24 gallon pumper for pulling a pool off the floor before the cleanup starts.
The Sandia Sniper 24-Gallon 2-Stage Flood Pumper (80-6001) is listed at $2,892. Sandia's spec sheet lists a 2-stage vacuum motor rated at 110 in of water lift and 120 CFM, a 3/4 HP waste pump with a 40 GPM pump-out rate and an auto pump-out that "works continuously, automatically dumping water so tanks don't have to be emptied when full." It draws 14.3 amps at 115 volts on a 25 ft, 12/3-gauge cord and comes with a 25 ft vacuum hose and a 25 ft dump hose, both 1-1/2 in. Dry weight is 106 lb, so plan on two people on steps. Sandia's warranty: lifetime on the body, 2 years on the vacuum motor, 1 year on the pump and all electrical components and 90 days on tools and accessories. It is a corded machine, which matters on a job where the water may be near outlets; run it from a GFCI protected outlet.
Pros
- Continuous pump-out at a rated 40 GPM through the 25 ft dump hose, so the 24 gallon tank does not need emptying.
- Sandia rates it for liquid, sludge and solids up to 1/2 in.
Cons
- Heavy at 106 lb dry weight.
- Draws 14.3 A, so little else can share that circuit.
Skip it if the job is a few square feet of water. A smaller extractor or wet vacuum is easier to carry, and our guide to using a shop vac for water covers when each is the right tool.
Step 5: the main dehumidifier
LGR dehumidifier
$3,079
The workhorse for Class 2 and Class 3 drying once the cleanup is done.
The XPOWER XD-130Li is an LGR (low grain refrigerant) dehumidifier. XPOWER rates it at 125 pints per day at AHAM conditions (80°F and 60% RH) and 220 pints per day at saturation (90°F and 90% RH). Those two numbers use different test conditions, so do not compare one with the other or with a figure that has no condition stated. It draws 8.2 A at 115 V, rates 420 CFM, weighs 90.4 lb and has a 40 ft drain hose and a 25 ft power cord. It has Bluetooth connection through the XPOWER Connect app and carries a 1 year limited warranty.
Pros
- Wheels and a handle on a 90.4 lb unit.
- 8.2 A draw is modest for a machine of this size.
Cons
- Size it on the 125 pint AHAM figure. The 220 pint figure holds only at 90°F and 90% RH.
- It is not a desiccant, so it loses ground in cold spaces.
Skip it as your single dehumidifier in an unheated, cold space, where a refrigerant unit loses capacity. A desiccant such as the DD400 below suits that job. On Class 4 dense materials it still serves as the low grain unit, often alongside a desiccant, as the drying table shows. Browse the LGR dehumidifiers collection for other sizes.
Step 5: the airflow
Low-profile air mover
$356
1,150 CFM with built-in GFCI outlets so units can be daisy-chained.
The XPOWER XL-760AM is a low-profile air mover. XPOWER lists a rated airflow of 1,150 CFM, a 1/3 HP sealed motor, 2.8 A at 115 V and a 15 ft cord. It weighs 20.7 lb, has one speed and units stack up to 6 high for storage. The built-in GFCI outlet lets you chain units from one wall outlet. Check the limit printed on the unit's rating label before you chain, and make sure the whole chain fits the wall circuit.
Pros
- Low 2.8 A draw per unit.
- Light at 20.7 lb and stackable.
Cons
- One speed only.
- A 15 ft cord is short, so plan outlet spacing.
Skip it if you only need a fan to move air in an open room. See all of the low-profile air movers we carry for other sizes and prices. Placement is covered in how to dry wet carpet.
Class 4: the desiccant unit
Desiccant for Class 4
Ebac DD400 Commercial Desiccant Dehumidifier 10500SS-US
$4,867 · 5.0 from 1 review
Works in cold rooms down to -4°F. Needs a duct (not in the box) to vent the wet air outside.
The Ebac DD400 is a desiccant dehumidifier. Instead of cooling coils it uses a rotating silica gel wheel, so it keeps working in unheated spaces; its listed lowest operating temperature is -4°F. Ebac's owner's manual gives its capacity as 71.5 pints per day at 27°C (about 80°F) and 60% RH. The manual's capacity chart shows output falling as the incoming air gets colder and drier, so expect less than that in a cold room. The manual also says the warm, moist reactivation air must be vented outside the building through a duct, and that the unit needs 0.5 m (about 20 in) of clear space around its inlets and outlets. It draws 8 A at 220 to 240 V, so check the plug and the circuit before you bring it in. Weight is 59.5 lb and noise is listed at 67 dB.
It is one of our best-selling dehumidifiers. That does not mean it suits every job.
Pros
- Operates down to -4°F where a refrigerant unit struggles.
- Light at 59.5 lb with carry handles.
Cons
- Needs a duct run to the outside for the wet air.
- Runs on 220 to 240 V, not the standard 115 V outlet.
Skip it if the space is heated and the job is Class 1 to 3: an LGR unit is simpler to set up. The desiccant dehumidifiers collection has larger and smaller models.
Drying setup by class
| Class | Typical setup | Machines from this page |
|---|---|---|
| Class 1 | One dehumidifier and an air mover or two on the affected area. | One or two XL-760AM units with a dehumidifier sized to the room (smaller units are in the LGR dehumidifiers collection) |
| Class 2 | Extract, then an LGR dehumidifier and air movers along the wet walls and carpet edge. | XD-130Li with XL-760AM units |
| Class 3 | Several air movers plus one or more LGR dehumidifiers. More removal first. | Sniper pumper, XD-130Li and XL-760AM units |
| Class 4 | Low grain dehumidification of dense materials, often with a desiccant unit. | Ebac DD400 with XD-130Li |
Sizing is the hard part. Our dehumidifiers for water damage guide compares LGR, conventional and desiccant units and how many a job needs, and our dehumidifier sizing chart explains the pints per day ratings. To read the room's conditions as you dry, see how to read a psychrometric chart. For the full restoration lineup, shop the restoration dehumidifiers.
Getting more from the drying
- Measure first and measure again. Take moisture readings of the affected materials on day one and every day after, and stop only when they match a dry reference reading from an unaffected area.
- Keep doors and windows closed while dehumidifiers run, so you are not drying the outdoors.
- Point air movers along the wet surface, not at the middle of the room.
- Empty or drain the dehumidifier continuously. The XD-130Li lists a 40 ft drain hose for this.
- Use a hose or duct on a desiccant unit so the wet exhaust leaves the building.
If the loss follows a leak and you are worried about odor afterward, our guide to getting rid of carpet odor picks up from here, and if you suspect mold is already present, the mold remediation equipment guide lists the kit by job size.
Frequently asked questions
What is Category 3 contaminated water?
It is the most contaminated of the three S500 categories. The 2021 standard describes it as grossly contaminated water that can carry harmful agents and cause significant adverse reactions if people touch or swallow it. Sewage, wasteline backflows from beyond any trap, seawater flooding and rising water from rivers or streams are among its examples. S500 judges the category on the water's originating source and its quality after it contacts materials on the job, not on its color.
What is IICRC Category 2 water?
Category 2 is contaminated water that falls short of the grossly contaminated Category 3. For the work, S500 groups it with Category 3: remediation should come before restorative drying, with contamination controls and appropriate worker protection. Time and temperature can move it to a higher category.
Is water from an overflowing fixture bowl Category 3?
It depends on what overflowed. An overflow of clean water from a supply line is judged differently from an overflow that carries waste from a backed-up sewer line. S500 lists wasteline backflows that originate from beyond any trap, regardless of visible content or color, as Category 3, so a backup from the drain side is Category 3 even when it looks clear. Ask a qualified restorer to class it for your job, because the source decides the category.
What kind of water damage will insurance cover?
That depends on your policy and your insurer, and we cannot give legal advice. What helps any claim is a record: take photos, write down the date and the source and keep daily moisture readings while the drying runs. Our moisture meter readings chart shows how to read them.
What is the difference between a category and a class?
The category describes the water: how contaminated it is, from Category 1 to Category 3. The class describes the job: how much water there is and how hard it will be to evaporate, from Class 1 to Class 4. They are set separately, so a loss has both.
Can I dry Category 3 water damage myself?
Drying is the easy part and the cleanup is not. The cleanup comes first. S500 says remediation should occur before restorative drying for Category 2 and 3 water, with contamination controls and worker protection, so bring in a trained restorer for that stage. S500 also says an indoor environmental professional (IEP) should be retained when, for example, occupants are high risk individuals, a public health issue exists (elderly care or childcare facility, public buildings, hospitals), contaminants are believed to have been aerosolized or there is a need to determine that the water actually contains contamination.
What is remediation for water damage?
Under S500 section 10.6.7, remediation is the cleanup stage. For Category 2 and 3 water it comes before restorative drying and uses contamination controls and worker protection.
What should you do about water damage in a basement?
Stop the source first. Then judge the category from the source: a floor drain backup from beyond the trap is Category 3 under S500. Pull the standing water, take moisture readings of the walls and floor, then dry with a dehumidifier and air movers sized to the room.
Set up the drying
Related guides
- Dehumidifiers for Water Damage: LGR vs Conventional vs Desiccant and How Many You Need
- How to Read a Psychrometric Chart for Water Damage: GPP, Dew Point, Grain Depression
- Water Damage Restoration Process: The Steps Pros Follow From Extraction to Dry
- Sewage Backup Cleanup: Category 3 Water Steps, PPE and Equipment
