What level of free available chlorine is required for a fecal accident involving diarrhea or liquid stools?

In the case of a fecal accident involving diarrhea or liquid stools, the recommended level of free available chlorine is indeed 20 ppm. This elevated concentration is necessary because fecal matter, especially from diarrhea, can contain harmful pathogens that are resistant to chlorine disinfection at lower levels. The higher chlorine concentration is critical for effectively inactivating viruses, bacteria, and protozoan pathogens, such as Cryptosporidium, which can be particularly challenging to eliminate.

Maintaining this elevated level of chlorine for a specified duration ensures that the water is made safe for swimming again. The increased chlorine level creates a more aggressive disinfecting environment that helps break down pathogens and render them inactive. After this treatment, it is important to bring the chlorine levels back down to normal operating levels (typically around 1 to 3 ppm) before allowing swimmers to re-enter the pool. This protocol is essential for public health and safety in swimming facilities.