Which statement correctly describes the required range of disinfectant (FAC) and bromine in public pools?

• A. Indoor pools require FAC 0.5-1.0 ppm; Outdoor pools require FAC 5-10 ppm
• B. Indoor pools require bromine 2-4 ppm; Outdoor pools require bromine 2-4 ppm
• C. Bromine is not used in public pools
• D. Indoor pools require FAC 0.5-10 ppm and Outdoor pools require FAC 1-10 ppm; bromine 2-4 ppm

Answer: (D)

Maintaining disinfectant residuals at safe, effective levels is essential for pool safety. Free available chlorine (FAC) is the primary sanitizer in chlorine-based pools, while bromine is another popular sanitizer used in brominated pools. The ranges shown—FAC kept indoors between 0.5 and 10 ppm, outdoors between 1 and 10 ppm, and bromine kept at 2–4 ppm—reflect real-world adjustments for different environments and usage. Outdoor pools face more rapid chlorine loss from sunlight and higher turnover, so starting a bit higher helps maintain disinfection; indoor pools can operate with a slightly wider acceptable range without over-chlorination. Bromine’s 2–4 ppm range provides a reliable disinfection level under varying pH conditions. The other statements either misstate these ranges or claim bromine isn’t used, which doesn’t align with common pool practices.