Understand the three water categories in plain English, what to keep or toss, the right PPE, and how to avoid mold and insurance headaches.
Quick TL;DR
- Category 1 (“clean”): From sanitary sources (e.g., supply line). Lower risk initially, but degrades to higher categories if not dried fast or if it contacts dirty surfaces.
- Category 2 (“gray”): Contains contaminants (detergents, microorganisms). Can make you sick; needs thorough extraction, drying, and disinfection. Often escalates to Cat 3 if ignored.
- Category 3 (“black”): Heavily contaminated (sewage, river/ground floodwater). Health hazard. Porous materials are usually discarded; pros should handle it.
- Time matters: Drying within 24–48 hours is key to suppress mold growth.
Why the Category Dictates Your Cleanup
Categories aren’t about how “wet” things are—they’re about contamination and health risk. The same amount of water means very different cleanup rules depending on whether it’s a clean supply-line leak (Cat 1), a soapy dishwasher overflow (Cat 2), or a sewage backup or flood (Cat 3). Industry standards use these categories to decide PPE, what to remove, and when professional remediation is required.
Important: “Clean” water doesn’t stay clean. As hours pass and water wicks through building materials, it picks up soils and microbes—often moving from Category 1 → 2 → 3 if you don’t dry promptly.
Category 1 Water (Clean): Examples, Risks & Cleanup
Typical sources: Broken hot/cold supply lines, toilet tank, rain that enters directly (before touching soil), melting ice.
Risks: Initially low risk, but hidden moisture can breed mold if not removed quickly; clean water can degrade within 24–48 hours, especially in porous materials.
What cleanup looks like:
- Stop the source, extract standing water, set dehumidifiers + air movers, and contain the wet area so humidity doesn’t spread.
- Pull wet carpet pad if saturated; many carpets can be saved.
- Open assemblies strategically (baseboards off, small weep holes) to dry wall cavities; verify with moisture meters, not just “feels dry.”
- Disinfect non-porous surfaces if needed; the priority is drying everything to standard.
DIY vs. pro: Small, well-defined Cat 1 spills are often DIY with proper drying gear. If multiple rooms are wet, ceilings sag, or drying stalls, bring in a mitigation pro.
Category 2 Water (Gray): Examples, Risks & Cleanup
Typical sources: Dishwasher/washing machine overflows, sump failures, toilet overflow without solids, aquariums/waterbeds. Contains chemicals or microorganisms that can cause illness.
Risks: Higher exposure risk; materials hold contaminated moisture. If neglected, Cat 2 can escalate to Cat 3.
What cleanup looks like:
- Rapid extraction and aggressive dehumidification.
- Remove porous materials that are contaminated and slow to disinfect (e.g., saturated carpet pad, wet insulation, lower drywall via 12–24″ flood cuts).
- Clean and disinfect non-porous surfaces; keep HVAC off in the affected zone to prevent spreading humidity/contaminants.
- Continue daily moisture/relative humidity checks until you hit dry-standard.
DIY vs. pro: Usually pro-directed. If you do any work yourself, use PPE and limit to non-porous surface cleaning and moving contents out of the wet zone.
Category 3 Water (Black): Examples, Risks & Cleanup
Typical sources: Sewage backups, river/stream flooding, storm surge, groundwater intrusion, or any water left to stagnate for days. Highly contaminated; exposure can be dangerous.
What cleanup looks like:
- Professionals only with appropriate PPE, containment, negative air, extraction, and informed decontamination practices.
- Remove and discard most porous building materials and contents (carpet, pad, drywall, insulation, many upholstery items).
- Clean and disinfect non-porous surfaces; dry to target; verify with measurements before rebuild.
Re-entry & re-occupancy: Wait until authorities/pros confirm no structural/electrical hazards and remediation is complete—then rebuild.
Mold Timeline & Why Speed Is Everything
Public health guidance is blunt: dry everything within 24–48 hours to reduce the chance of mold. If you couldn’t dry in that window, assume mold and escalate accordingly.
Bleach notes: Never mix bleach and ammonia; ventilate when using cleaners. Bleach is appropriate only in some situations and mostly on non-porous surfaces; always clean dirt first—disinfectants don’t work through grime.
Safety First: PPE & Entering the Space
- General cleanup PPE: Waterproof boots, gloves, eye protection; long sleeves/pants. Extra caution with unknown chemicals in floodwater.
- Sewage/Category 3: Rubber gloves/boots and face protection are common minimums; selection depends on the task and exposure. When in doubt, defer to trained remediation teams.
- Before you go in: Confirm no electrical/gas hazards; in significant floods, wait until officials say it’s structurally safe.
What to Keep vs. Toss (Fast Matrix)
| Material/Item | Cat 1 | Cat 2 | Cat 3 |
|---|---|---|---|
| Drywall | Often save with fast dry; open cavities as needed | Usually flood cut 12–24″ | Remove |
| Insulation | Remove if saturated | Remove | Remove |
| Carpet | Often save; remove pad if soaked | Carpet sometimes saveable; pad discard | Discard |
| Hardwood | Often save with specialty drying | Case-by-case | Sometimes save with specialty drying; assess contamination |
| Laminate/pressboard | Often discard if swollen | Discard | Discard |
| Upholstery/mattress | Maybe if minimally damp | Usually discard | Discard |
These rules align with public guidance to discard items that cannot be cleaned/dried quickly, especially after flood/sewage events.
The 10 Biggest Mistakes (and easy fixes)
- Waiting for things to “air dry.” Hidden moisture = mold. Use dehumidifiers and verify with meters.
- Cleaning first, drying second. Do both, but drying cannot wait.
- Running HVAC too soon. Can spread humidity/contaminants.
- Bleach on everything. It’s not for porous materials and never mix with ammonia.
- Keeping contaminated porous items. With Cat 2/3, many porous materials must go.
- Skipping PPE. Even Cat 2 can make you sick; suit up.
- No documentation for insurance. Photograph, inventory, and log daily.
- Not isolating wet rooms. Use containment to keep humidity from spreading.
- Starting rebuild before dry-standard. Trap moisture → odors & mold.
- DIY’ing Category 3. This is professional work with real health risks.
DIY vs. Pro: A Simple Decision Tree
- Small, clean-water spill in one room, dried within 24 hours? DIY likely fine.
- Multiple rooms, wet wall cavities, or any Cat 2? Get a mitigation pro to set the plan.
- Any sewage/river/groundwater (Cat 3), structural/electrical issues, or delayed drying >48 hours? Hire professionals for remediation and clearance.
FAQs
Does Category 1 water always stay “clean”?
No. As it interacts with materials and time passes, it can degrade to Cat 2 or 3. Act fast.
How fast can mold appear?
Guidance says 24–48 hours is the critical window to dry.
What PPE should I use for cleanup?
At minimum: waterproof boots, gloves, eye protection, long sleeves. Higher-risk tasks may need more. For sewage events, defer to trained pros.
Which items should I throw away after a flood?
If you can’t clean/dry quickly—especially mattresses, carpet padding, stuffed items, and many porous contents—discard them.
