How much free chlorine should be added to achieve breakpoint chlorination?

Breakpoint chlorination is a critical process used to effectively eliminate combined chlorine (chloramines) present in swimming pools and water systems. The purpose of achieving breakpoint chlorination is to convert the combined chlorine into free chlorine, thereby improving water quality and sanitation.

To reach the breakpoint, experts have determined that you need to add a certain amount of free chlorine relative to the existing levels of combined chlorine. The correct measure is ten times the existing combined chlorine level. This significant ratio is essential because it ensures that there is enough free chlorine to overcome the chloramines and oxidize them completely. Once this threshold is reached, any additional free chlorine will begin to develop a measurable increase in free chlorine levels, effectively removing the compounds that cause odors and irritation during swimming.

This concept is rooted in the chemistry of chlorination, where the goal is not simply to add chlorine but to ensure enough is added to fully react with and eliminate unwanted chloramines. Understanding this principle is vital for pool operators to maintain high water quality and safety for users.