Category 3 Black Water: A Biological Hazard
A sewage backup is never a standard water leak.
The IICRC strictly classifies this as Category 3 Black Water. This liquid is grossly contaminated with harmful pathogens, bacteria, and human waste.
You must never clean this with a mop. Category 3 water rapidly soaks into drywall, baseboards, and subfloors. Any porous material touched by sewage becomes an active biohazard.
Handling this waste requires strict OSHA-compliant personal protective equipment (PPE).