I have a 35,000 gallon vinyl liner pool. It will not maintain a chlorine level. It's been shocked several times with as much as 13 bags of chlorine at a time. I have even used chlorine free shock one day and then chlorine shock the following day with the same result. Water test shows: FC: 0 TC: 0 Calcium hardness: 220 CYA: 40 Total Alkalinity: 80 pH: 7.4 Copper: 0 Iron: 0 Total Dissolved Solids: 1000 Phosphates: 100 I have had the water tested at two pool supply stores and the results are the same. They offered a few suggestions which I did and yet the results are the same. Any help/suggestions would be greatly appreciated. I live in Churchville, PA. a mostly residential neighborhood.