Certified Pool Operator Practice Test 2025 - Free Pool Operator Practice Questions and Study Guide

When chlorine is added to pool water, it reacts with nitrogen-based compounds such as urea or ammonia from sweat, urine, and other bodily fluids to form combined chlorine compounds. This process is known as chlorine degradation. The remaining chlorine in the pool is then able to effectively sanitize the water and prevent the growth of harmful bacteria and algae. Options B, C, and D are incorrect because they do not accurately describe the process of chlorine reacting with nitrogen-based compounds to form combined chlorine. Chlorine stabilization refers to the process of maintaining a consistent level of free chlorine in the pool water, while chlorine threshold is the level of chlorine needed to effectively sanitize the water. Chlorine breakpoint is the point at which all contaminants in the water have been oxidized by chlorine and the water is considered safe to swim in. However, this term is typically used in the context of shock/chlorine treatment and does not specifically describe the process of chlorine reacting with nitrogen-based compounds. Therefore, A is the most accurate choice.