No Chlorine holding this winter

Hello everyone. I religiously maintain my pool chemistry, and over the last couple of weeks, my chlorine has been nonexistent. I have a 20,000 gallon pool that uses UV light and a duoclear cartridge for sanitization, so I don't need much chlorine at all. That said, I can no longer get it to register, even after dropping extra trichlor tabs and increasing the rate to max. Pool looks crystal clear, pH is and always has been on the high end at 7.7-7.8, TA is 90, CH is 375, CYA is about 65. I'm...

Read more