A section of a water main pipe has been repaired and must be back in operation within 12 hours. The section shall be filled with a water/chlorine solution containing how many parts per million of chlorine?

The correct amount of chlorine to use in a water/chlorine solution for disinfection after a repair is typically 200 parts per million (ppm) for a section of a water main pipe. This concentration is effective in ensuring that the repaired section is properly disinfected and free from harmful bacteria and pathogens before being put back into service.

Using this concentration ensures compliance with public health standards, which mandate effective disinfection practices to maintain water quality and safety. Following the appropriate procedures, including allowing adequate contact time for the chlorine to work, is essential for successful disinfection. The chosen level of 200 ppm strikes a balance between efficacy and safety, making it the appropriate choice to ensure that the water main is both safe for operation and compliant with health regulations.