My CYA is no the high side (100) My problem is that my chlorine reading is 0 even after filling the clorinator to full and wide open on #5 then also adding 4 tablets to skimmer have been running the pump 24/7. Still no chlorine reading. Pool is clear and beautiful. FC is 0 CC is 0. ph is 7.2 TA is 100 CH is 160. One pool supply tells me to do nothing but wait for the TC to raise (it has been 10 days without getting a reading but did get to .03 one day) another pool supply says to drain 1/3 of the water and refill to lower the CYA. This I understand and also understand that the higher the CYA the more higher TC needed to sanitize. But I do not get why I show no TC at all. Where is all the chlorine going? I use Triclor and at first suspected that it had lost it's shelf life so the pool supply replaced it. When I put the knew pucs in the chlorinator the FC was 4 the next day but the following day it was 0. Also replaced the reagents. So the questions are..why am I not getting a reading, or what is eating the chlorine and if I go ahead and drain and refill getting the CYA down can I then expect to get a chlorine reading? Do I need to shock or drain and refill or do both? Nobody at either pool supply really knows the cause or what to do.