It is often safe to stay in a house after a sewage backup if the backup is small, confined to one room and closed off from the rest of the home. Leave if sewage covers a large area or cannot be contained, or if someone living there is very young, elderly, pregnant, ill or has a weakened immune system.
The risk is the germs, not the smell. New York City’s sewage backup guidance names bacteria, viruses and parasites in untreated sewage as the main concern. Contact can cause nausea, vomiting, diarrhea and skin infections, and children, older people and anyone with a weakened immune system face higher risk.
If you stay, treat the affected room as off limits. Keep children and pets out, and wear rubber gloves and boots if you have to go in. Turn off power at the breaker if water is near outlets or appliances, and shut off forced air heating or cooling if sewage reached the ductwork. Stop running water until the line is cleared, since every flush adds to the sewage coming up through the lowest drain.
Porous things that sewage soaked cannot be made safe again. Carpet and pad, mattresses, upholstered furniture, stuffed toys, food and medicine all go, and wet drywall is cut out above the water line. A backup that reaches several rooms is a job for a professional cleanup crew, and it can damage floors and walls well beyond the first stain.
The room is ready to use again once the sewage is gone, hard surfaces are washed and disinfected, soaked materials are out and everything is dry. One limit: cleaning does not fix the cause, and the line can back up again until it is cleared. See a doctor if anyone gets nausea, vomiting or diarrhea after contact.