I have been using the methods here for approx. 3 years with pretty good success. I have been running a CYA level of about 35-40 and decided to bump it up a bit for the intese summer sun here in Mesa, AZ. Using my older Taylor test kit I read 0 levels even after adding 2.5 lbs. of CYA. I then took a water sample to Paddock Pools and they confirmed a 0 level. Then I took water samples to 3 nearby Leslies Pool Stores and all 3 read levels between 60 and 80! Then I ordered a TF-100 kit and it reads 0 CYA. All other parameters are good except CH which is over 1300. It's too hot to drain and fill so I may have to live with that until fall. Any ideas or suggestions would be appreciated.