I have a 15k inground W/vinyl liner. Always kept in excellent condition, have had it 15 years. Always used daily non stabilized tabs at the recomendation of the installer. Three years ago, got lazy started using 3 inch stabilized (7 day) tabs. with intermiitant shocking as needed (after large groups of swimmers) 3 weeks ago, I noticed both chlorine readings very high. TC and FC at 10 PPM, and no sign of them coming down. Water looks and feels perfect. No chl smell. I'm guessing the water is over stabilized, and I have no choice but to drain most and refill. I'm posting here to see what others think before I do someting even dumber than not listening to some (the pool installer) who I really do trust. Othere reading; Total Hardness 250, PH 7.2 Total Alk 80 CA 40... HELP!