I have a 20x48 intex ultra frame with an intex 2500/gps sand filter. Location is Midwest. Any suggestions on how to winterize? Chemical prep/pump/filter storage etc..... I have closed it down before but with the cartridge filter so it was easy enough to take inside. I have left the pool up the last two years but I've never really opened up to a clean pool in the spring so I need to do something different with the winter prep. Thank you!