I replaced my standard tank with a captive air tank last summer. The standard tank had a draincock so that I could drain the water at the end of the season before winterizing my summer home. The captive air tank has no draincock. I depressurized everything, blew back the lines with compressed air and drained the water pump. It gets below freezing and I don't know what else to do. I assume there is still water remaining in a captive air tank.