We have an in ground gunite pool (18,000 gallons) that is 15 months old with an aqua pure salt system. I had a service error "HH" yesterday so I decided to check the salt cell this morning. It had quite a bit of scale built up so I cleaned it thoroughly with the water/acid mix. The cleaning removed all of the scale. I put it back into service and I'm getting a low salt reading / alarm now. It's reading 0.6-0.8, and it was reading 3.1 the day before yesterday. I took a water sample to the local pool store and the result was 3.1, which leaves me scratching my head. Obviously, the salt water generator will not produce chlorine with the salt reading where it is now. Should I replace the sensor or should I recalibrate the salt cell? If calibration is an option, what is the procedure? I can't find it in any of the aqua pure literature.