There is Total Chlorine (TC), Free Chlorine (FC), and Combined Chlorine (CC). TC is the sum of FC and CC. FC is the one responsible for disinfecting the pool. CC, also known as chloramine, is a used up chlorine and is the one that causes cloudiness; this should always be 0 ppm for a very clear pool. This means that your Free Chlorine should always be 3 ppm. In some cases, FC may drop, but it should not go down passed 2.5 ppm, a level at which CC is 0.5 ppm and is still OK for swimming. When CC goes higher than 0.5 ppm, that is not OK for swimming since FC is too low and the water will not be disinfected.