Maybe Janet has already mentioned this to you in your thread and I just missed it when I scanned through it but you need to buy a good kit. Especially if your CYA is over 100 like you think it is, you'll have to run higher chlorine levels than the kits you'll be able to buy locally will be able to test. You need to buy the Taylor K-2006 or 2006C kit which you can find in Janet's (Aylad) signature block in post #2 above. It can register chlorine levels up to around 50ppm I think as opposed to around 5 like most kits.