Hello out there, I am new to TFP and I am here hopefully to run the problem I am having across the experts. Here it goes: I have a 20x40 inground pool which holds about 30000 gallons. I have had the pool since 2003 and it is clorinated with the LM2-40. All the years I've had it, I have always been able to make a ton of chlorine keeping it set on the 2 to 3 LED postion and filtering 12 hours a day except for shocking. This year is different, with the chlorinator set as high as it can go, I can't hardly get a chlorine reading. My water is chrystal clear though, the ph is at 7.2 to 7.4. Total alkylinity was low so I brought that up into range. My total hardness looked like it was at zero, so I brought that up to about 200ppm. Lastly, CYA is on the low side, but my pool chemical store is suggesting getting all the other chemicals perfect before adding CYA. The question after all that is, how do you know if you need to replace the cell. My cell is from 2003, 7 years old. Could that be the problem. One last thing, my pool water rand a little low from evaporation, I added about an 2 inches of city water. The next day, my stairs were stained rust alomg with all my jets, skimmers and main drain. The pool place checked for iron and copper. Both were good. Any suggestions will be greatly appreciated.