You cannot have "Chlorine Lock" with a CYA level of 10. To add to what Ben said, "Chlorine Lock" is a false name for the condition that occurs when CYA, ie stabilizer levels are too high for "normal" chlorine levels (ie, FC3ppm or less) to work. This usually happens when someone has used nothing but Tri-Chlor pucks and their CYA level is well over a 100 ppm but are trying to maintain chlorine at 3 to 5 ppm. The answer is simple: Higher levels of chlorine, 8-15 ppm. But with a CYA of 10, that's not possible. So back to Ben's "(a)"--they haven't a clue. As he said, "Chlorine Lock" doesn't exist.