Certified Pool Operator Test 2025 – 400 Free Practice Questions to Pass the Exam

When measuring chlorine levels in a pool or other water source, there are typically two types that are measured Total Available Chlorine (TAC) and Free Available Chlorine (FAC). TAC includes both the chlorine that is currently working to sanitize the water and the chlorine that has already finished sanitizing and is no longer active. FAC, on the other hand, only measures the chlorine that is currently active and working to sanitize the water. So in this scenario, where the TAC is 1.6 and the FAC is 1.5, it means that 1.5 parts per million (ppm) of the 1.6 ppm total chlorine is currently active and working. Therefore, the remaining 0.1 ppm is the Combined Chlorine level, which is the amount of chlorine that has already done its job and is no longer active. This is why the correct answer is A. The other options are incorrect because they either do not take into account the TAC and FAC levels or they do not reflect the remaining amount of Combined Chlorine.