What does high chlorine demand indicate?

High chlorine demand indicates the presence of a high level of contaminants in the water. When there are more impurities—such as organic matter, including leaves, algae, and bacteria—chlorine is used up more quickly to sanitize and oxidize these substances. This means that for the water to maintain its sanitary condition and remain clear, more chlorine must be added to meet the increased demand. A higher chlorine demand is often an indication that the water requires treatment to reduce the levels of these impurities to ensure the health and safety of swimmers.

In contrast, low levels of impurities would typically result in a lower chlorine demand, and effective chlorine stabilization refers to maintaining chlorine levels for consistent disinfection, not an indicator of demand. Meanwhile, improper water balance could affect sanitizer efficacy, but it is not directly synonymous with high chlorine demand.