What chlorine concentration is recommended for spraying or painting the inside of a water storage tank for disinfection?

The recommended chlorine concentration of 200 mg/L for spraying or painting the inside of a water storage tank for disinfection is based on its effectiveness in killing a wide range of microorganisms, including bacteria, viruses, and protozoa. This concentration achieves a balance between ensuring thorough disinfection while also being safe for the water system when properly rinsed and allowed to ventilate.

Using a concentration that is too low may not effectively eliminate pathogens, potentially compromising water quality. Conversely, concentrations that are too high could lead to residual chlorine levels that exceed safe drinking water standards once the tank is put back into service. Therefore, 200 mg/L serves as a practical and accepted concentration that is effective for disinfection without adverse effects on the water supply.