How is combined chlorine defined?

Combined chlorine is defined as the amount of chlorine that is not available for disinfection because it has reacted with ammonia or organic nitrogen compounds, forming chloramines. The correct way to calculate this is by taking the total chlorine level in the water and subtracting the free chlorine level. This means that combined chlorine is a measure of the chloramines formed through the reaction of free chlorine with various contaminants in the water.

Understanding total chlorine, which includes both free chlorine (the chlorine available to sanitize) and combined chlorine, is critical for pool operators. When free chlorine diminishes due to its reaction with contaminants, the combined chlorine levels rise, which may indicate poor water quality and can lead to unpleasant odors and irritation for swimmers. Therefore, monitoring these levels ensures effective pool sanitation and clarity.