Last year I didn't close the pool for the winter. I basically raised the cya up a bit and kept it slightly chlorinated. I continue to monitor ph and chlorine thru the winter but not as much as during the pool season. I didn't drain the filter, i would still run it once a week and also if they were expecting the temps to drop below freezing. Temps around here don't usually fall below 30 for more than a few days at a time. Could this cause any problems? I need to know before i do this again this winter.