Ever since I replaced my cartridge filter with a Hayward sand filter (about a year ago), the pool water has been very cloudy. It was ok last summer and I was hoping it would clear up over time, but it has not. I religiously check the pool chemicals, and everything seems normal except the calcium is high. A couple of weeks ago I decided to get serious about this, so I measured the hardness in the pool and it was at 380. I measured the hardness at the spigot where the auto filler taps in, and the hardness was zero. Then I back washed the sand filter for five minutes (Hayward recommends 2 minutes) which dropped the water leverl about 3-4 inches. Let the pool fill up and there is very little difference (if any) in clarity. The hardness two days ago was at 370. Any suggestions?