ATLANTA — Residents and businesses in southwest Atlanta, South Fulton, Fairburn and Union City were told Monday, Oct. 12, to boil tap water before using it after a supply interruption affected the Chattahoochee Water Treatment Plant. The Atlanta Department of Watershed Management said the advisory was issued as a precaution and in line with Georgia Environmental Protection Division public-notice guidance. Crews and contractors were sent to the plant to investigate while the department monitored water-system pressure and operations. Until the advisory is lifted, customers should use bottled water or boil tap water before drinking it, brushing teeth, washing or preparing food, making ice, preparing infant formula or giving water to pets. Bring water to a boil for one minute, then let it cool before use. The department also warned people not to drink from public water fountains in the affected area and urged extra caution for infants, older adults and people with weakened immune systems. The department said the advisory will remain in place until sampling protocols are completed and officials authorize its removal. No timetable for lifting it was provided.