I have the standard T15 cell and it was just replaced last year. The pool is 28,000 gallons. I will post the numbers later as I am not home right now. Best I can remember my CYA is only at around 50. I thought I should keep it as low as possible because last year I had an algae problem and had to raise the chlorine to around 15ppm (per instructions found here) in order to clear it. I thought the higher the CYA, the higher you had to raise the chlorine level in order to kill the algae. I use a DE filter, Aquarite SWG. When the Cell went bad last year, I had to call Goldline(Aquarite). They told me that I should expect to have to run the SWG at 90 percent or above and that 12 hours would be the min I chould expect to get away with. Most times when I check the FCL, it is only around .5 to 1.0 ppm.