A sewage backup pushes water from the drain system back into the house, usually through a toilet, a tub or a floor drain at the lowest fixture. Older neighborhoods here still carry clay and cast iron sewer laterals, and the roots of mature trees find the joints. Once a lateral is blocked, every flush and shower in the house adds to the backup.
Why sewage is never just dried
Sewage carries bacteria and viruses, so the IICRC S500 standard treats it as Category 3 from the start. Carpet, pad, lower drywall, insulation and anything else porous that it touched are removed and bagged, not dried and kept. Hard surfaces such as tile, concrete and framing are cleaned and treated with an EPA-registered antimicrobial, left on for the dwell time on its label.
How the cleanup is done
- The area is sealed with plastic containment and kept under negative air with HEPA air scrubbers
- Workers wear gloves, boots, eye protection and respirators at minimum
- Standing sewage is extracted, and porous materials above the high-water mark are cut out
- Surfaces are cleaned and treated, then dried and verified with meters
The EPA overview of sewer overflows explains why raw sewage is a health hazard and not a cleaning job for a mop and bucket.
Stop using water until the drain is cleared
While a lateral is blocked, every fixture in the house drains toward the backup. Stop running water, hold off on flushing and keep people and pets out of the area. A plumber clears or repairs the lateral, and the cleanup team handles the house. In the City of San Diego, the lateral from the house to the public main is the owner's to maintain, while a problem in the public main goes to City of San Diego Public Utilities.
If sewage reached a crawl space under a raised floor, the soil and framing there need the same Category 3 treatment as the rooms above.