Short answer
Category 3 water—black water—is grossly contaminated with sewage, heavy metals, toxic runoff, and pathogens common in Seattle storm surges and sewer backups. Unlike a clean pipe burst, it is biologically active and unsafe without professional PPE, containment, and hospital-grade disinfection before structural drying begins.
Dive deep
IICRC classification drives the entire restoration scope. Category 1 is clean supply water; Category 3 is the highest contamination tier. Storm floodwater picking up street waste, sewer backflows, and industrial runoff all qualify. Skin contact or inhalation without protection can cause serious respiratory and infection risk.
Our protocol uses EPA-registered disinfectants, negative-air containment, and removal of porous materials that cannot be sanitized. Structural surfaces—concrete and framing—get cleaned and treated before drying equipment runs. Entering a Category 3 flood with household gloves and a shop vac spreads contamination and skips the demolition scope porous materials require.
On site we confirm category, establish barriers, and document for insurance. Category 3 is never a “dry it out yourself” event.
When it applies
- Sewer backups and toilet overflows affecting the basement
- Street or storm floodwater entering the structure
- Any water with visible contamination, odor, or known sewage contact
- Insurance claims requiring proper biohazard classification
When it does not
- Broken supply lines on potable water (Category 1)
- Appliance overflow from clean source before contamination (may start Category 1)
- Gray water properly contained before escalation—still needs pro drying but different protocol
What we do next
We contain, remove unsalvageable materials, decontaminate structure, and dry to verified standards. For Category 3 floods, call our basement restoration team.
