Still a newish pool owner (about 5 months). And I'm in SW FL. I have a 10,000 gallon pool and over the winter my pool like clockwork needed 1 cup of pool store chlorine a day to maintain level. All of a sudden I noticed it kept dropping, so when it got down to 3ppm (normally kept it at 7.5 b/c cya level was around 60ish) I put 3 cups in. That should have brought it up to 7.5 by the next day but it didn't, the next day it still registered 3.0 chlorine. So I did a cya test and it looks like that is really down from where it was, I measured about 25ish now (the test is fairly subjective though depending on how good you eyesight is). So I added 9 cups to see what would happen, and again it looks like after 24 hours it is back down to 3 which I don't even understand b/c that is what 3 cups did?!?! Anyway not sure what to do, I'm thinking of throwing a few pucks in b/c after learning they added cya I stopped using them 5 months ago and it appears to have worked by lowering my cya quite a bit. Can anyone help me with this, not sure what to do. My pool has been so easy and predictable and now i'm getting weird readings for some reason and it appears my chlorine is just burning off. I haven't shocked the pool forever should I do that? Any help is appreciated.