Published August 29, 2026
Classifying the water correctly in the first ten minutes determines the equipment, the demolition scope, the cost, and whether residents can stay. Getting it wrong in either direction is expensive.
Category 1 — clean water
Source: supply lines, water heaters, appliance supply lines, rainwater that did not touch contaminants.
- Safe to extract and dry in place in most cases
- Drywall and insulation can often be dried rather than removed
- Residents typically stay
- Typical apartment cost: $900–$3,500
Important: Category 1 degrades. Clean water sitting in an apartment for 48 hours in warm conditions becomes Category 2. Time is the variable, not the source.
Category 2 — gray water
Source: dishwasher and washing machine discharge, toilet overflow with urine only, aquarium, sump overflow, or Category 1 that sat too long.
- Extraction plus antimicrobial treatment
- Wet carpet pad is removed; carpet may be salvageable
- Wet insulation removed; drywall often flood-cut 12–24 inches
- Residents usually stay if bathroom and kitchen work
- Typical apartment cost: $2,500–$7,500
Category 3 — black water
Source: sewage backup, toilet overflow with solids, ground surface water intrusion, river flooding, or Category 2 that sat beyond 48–72 hours.
- Everything porous in the affected area comes out: carpet, pad, insulation, affected drywall, often base cabinets
- Containment and negative air
- Residents relocated in almost every case
- Typical apartment cost: $6,000–$25,000+
Multifamily-specific traps
Stacked units. A Category 1 leak upstairs can become Category 2 or 3 downstairs if it passes through a wall cavity with old contamination or through a plumbing chase.
Shared laundry. Laundry-room discharge losses are Category 2 by default even though the water looks clean.
Garden level and slab. Ground water entering below grade is Category 3, regardless of how clear it is.
Sewage backups. Never in-house. Category 3 with pathogen exposure requires PPE, containment, and disposal handling — and creates real liability if handled casually.
Documentation that supports the category
Photograph the source, the water at its extent, and the category call. If you classify Category 2 and the adjuster reads it as Category 1, the difference is thousands of dollars of removed materials that will not be paid for. Write down the source, the discovery time, and the elapsed time before extraction started.
Minnesota timing note
Cold-weather losses degrade more slowly but hide longer, because water in an unheated cavity or exterior wall does not smell or show for weeks. Do not assume a winter loss is smaller — assume it is later.
Get the right response
We classify, contain, extract, dry, and rebuild — including drywall, insulation, flooring, and paint — so an apartment loss is one vendor from the first call through the final punch list.
Call 612-400-8036.
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Frequently asked questions
What is the difference between Category 1, 2, and 3 water?
Category 1 is clean supply water, Category 2 is gray water from appliances or urine-only overflow, and Category 3 is contaminated black water from sewage or ground water. Each requires progressively more removal, containment, and PPE.
Can clean water become contaminated?
Yes. Category 1 water typically degrades to Category 2 after about 48 hours and can reach Category 3 beyond 48 to 72 hours, so response time changes the category.
Should maintenance staff clean up a sewage backup?
No. Category 3 losses involve pathogen exposure and require PPE, containment, negative air, and proper disposal. Handling it in-house creates real liability.