Last few days, SWCG didn't make enough clhorine, I had to add chlorine every day. Didn't know why. Never crossed the thought of low salt level. Until yesterday, the SWCG appeared the code 91 (low salt level). Aha, dumb me. This afternoon, I added about 15 lb of salt. Let the sand filter ran itself about for 4 hr. Started the SWCG, the same code still there. Measure the salt level is at 3200 ppm. What is going on here?