Updated August 31, 2026. Field tickets and Vault readers already land on this URL. This guide is the water pillar on Restoration Intel — category/class, extraction, psychrometrics, drying goals, and documentation that stands up to a carrier review. It is not a homeowner DIY sheet.
Field FAQ (lift these first)
What is the difference between Category and Class of water?
Category describes contamination (what is in the water). Class describes how much water and how porous the affected materials are (how hard it is to dry). You need both on every job. Getting Category wrong creates a liability and health problem. Getting Class wrong creates an equipment and time problem.
Is weather-related water automatically Category 3?
No. The current book is ANSI/IICRC S500 Fifth Edition (2021). The February 10, 2026 Consensus Body position statement is clear: top-down water ingress, wind-driven rain, and weather-related events are not automatically Category 3. Gross contamination is the test — inspect, gather information, make a preliminary determination, then classify. Details live in the companion S500 field guide on this site.
How fast does secondary damage start?
S500 frames secondary damage risk in hours, not days. Microbial amplification potential, swelling, delamination, and Category escalation all climb with time and temperature. A loss addressed inside the first few hours is a different job than the same loss discovered at 48 hours. Document discovery time and arrival time on every ticket.
When do you demo versus dry in place?
Porous materials that cannot be restored to a pre-loss dry standard, or that hold Category 3 contamination in a way that cannot be cleaned to a safe end state, come out. Semi-porous and non-porous materials are evaluated against moisture readings, finish type, and contamination. If you cannot prove drying goals with instruments, you do not claim “dried in place.”
What belongs in day-one documentation?
Source stop confirmation, category/class with rationale, moisture map with unaffected reference readings, photos before demolition, contents inventory for affected rooms, equipment placed with counts, and the first psychrometric set (temp, RH, specific humidity / grains). Carriers and TPAs argue with thin files — not with complete ones.
The governing standard: ANSI/IICRC S500 (5th Edition, 2021)
ANSI/IICRC S500 is the standard of care for professional water damage restoration in the United States. It covers principles of restoration, microbiology and health effects, building science, psychrometry and drying technology, antimicrobials, safety, administrative procedures, inspections and preliminary determinations, structural and HVAC restoration, contents, and large-loss projects.
There is no published “August 2026 edition” of S500. When field staff or adjusters cite a 2026 book, point them to the Fifth Edition plus the Consensus Body position statement on weather-related category — not to a nonexistent rewrite.
Categories of water (contamination)
Category 1 — water from a sanitary source that does not pose substantial risk from contamination at the time of discharge (examples often include supply-line breaks before contact with contaminants). Category can escalate with time, temperature, and contact with soils or sewage.
Category 2 — significant contamination; can cause discomfort or sickness if contacted or consumed. Common examples include discharge from washing machines / dishwashers with detergent soils, toilet bowl overflow with urine (no feces), and sump failures with known contaminants.
Category 3 — grossly contaminated water containing pathogenic, toxigenic, or other harmful agents. Sewage, toilet overflow beyond the trap with feces, seawater, rising flood water with contaminants, and water that has contacted toxic materials fall here. Category 3 changes PPE, demolition scope, and contents decisions.
Always reassess Category as conditions change. A Category 1 loss left standing can become Category 2 or 3. Write the reassessment into the daily log.
Classes of water (amount and porosity)
Class describes the quantity of water and the porosity of wet materials — which drives dehumidifier sizing and drying time:
- Class 1 — least water; wet materials are low-porosity or limited in area.
- Class 2 — significant water; wet carpet and cushion, or water wicked up walls (typically under ~24″), with mid-porosity materials involved.
- Class 3 — greatest water from overhead; ceilings, walls, insulation, carpet, and cushion may all be wet.
- Class 4 — specialty drying (hardwood, plaster, concrete, stone, crawlspaces) where bound water and low evaporation rate dominate.
Mis-classing a Class 4 hardwood floor as a quick Class 2 carpet job is how callbacks and mold claims get born.
The response sequence (field order)
- Safety and source control — electrical, structural, slip hazards; stop the water.
- Inspection and information gathering — interview, history, weather/plumbing context.
- Preliminary determination — Category, Class, affected materials, HVAC involvement.
- Pre-mitigation documentation — photos, moisture map, contents notes.
- Extraction — remove bulk water; do not skip extraction and hope equipment will “pull it.”
- Controlled demolition — remove what cannot be restored; contain Category 3 work.
- Drying system setup — air movers + dehumidification sized to Class and chamber.
- Daily monitoring — psychrometrics + moisture readings until goals met.
- Verification and closeout — EMC relative to unaffected references; final file for carrier/TPA.
Psychrometrics and drying goals (what “dry” means)
Drying is not “feels dry.” It is instrumented. Record temperature, relative humidity, and humidity ratio (grains / specific humidity) for the affected chamber and for outdoor or unaffected control air as your job requires. Place air movers to disrupt the boundary layer on wet surfaces. Size dehumidification so the system can actually lower vapor pressure in the air.
Drying goals are met when affected materials return to equilibrium moisture content consistent with unaffected reference materials of the same type — and stay there under monitored conditions. If readings stall, change airflow, heat (within safe limits), containment, or equipment — then document why.
Residential vs commercial water losses
Residential jobs often hinge on response time, contents, and homeowner housing. Pipe bursts, supply-line failures, appliance discharges, and toilet overflows dominate volume. Companion deep-dives on this site cover pipe-burst-to-move-back sequencing.
Commercial / large-loss jobs add occupancy, multi-trade coordination, AHU/HVAC decisions, after-hours work windows, and project management. Same S500 science — larger chambers, more documentation, more stakeholders.
Insurance and TPA documentation that holds
Scope language should track Category/Class, materials removed vs dried, equipment days, and daily monitoring. Photo sets must show before demo, during mitigation, and dry-standard verification. When a TPA challenges drying days, your psychrometric and moisture logs are the answer — not a paragraph of adjectives.
Scope of coverage on Restoration Intel
Use this pillar with:
- Water Damage Categories and Classes: IICRC S500 Field Guide
- Storm and flood water intrusion: extraction and drying protocol
- Residential water damage: pipe burst to move-back
- Commercial water damage: large-loss protocol
- Mold remediation: the complete professional guide
Frequently Asked Questions
What is ANSI/IICRC S500?
The ANSI-approved Standard for Professional Water Damage Restoration. Fifth Edition (2021) is the current published edition.
How long does water damage restoration take?
Mitigation and drying often run several days of monitored equipment time after extraction and any demolition. Rebuild is separate. Class 4 and Category 3 jobs routinely run longer.
Does homeowners insurance cover water damage restoration?
Coverage depends on the policy and the cause of loss (sudden and accidental discharge vs long-term seepage, flood endorsements, etc.). Restorers document the loss; coverage determinations belong to the carrier. Do not promise coverage on a marketing page or a ticket.
When should mold remediation enter a water job?
When conditions support amplification or visible growth is present, bring S520 judgment and containment discipline. Moisture control first — then microbial scope. See the mold pillar on this site.