I will close my pool on Sunday for the season. Recent tests show all levels within appropriate ranges. With pH of 7.8 and water temp of 55, I get a CSI of -.17. As water temp drops, Pool Math shows that CSI also drops. If I lower pH to 7.6, CSI drops even more. Should I just leave the pH where it's at and proceed with closing? Also.... what's the lowest water temp I should enter in Pool Math to get an accurate CSI for the winter months?