Can CYA reagent go bad? I have been running 50 all season and last tested about 3 or 4 weeks ago. Today I tested CYA and the dot never disappeared. I had a mishap today that turned out OK and I was lucky. I needed to add a couple of inches of water so I turned on the hose an hour before I needed to leave for work. I forgot to turn it off and went to work. I came home at lunch, which I never do, and found the water within an inch of overflowing. All day would have made a big mess! Anyway, I dumped a bunch of water by running the filter to waste, reducing about 5 inches of water to the proper level. I know that couldn't wipe out my CYA. The only explanation I have is that the reagent went bad. Any other ideas?