I know I'm getting ahead of myself here, but I like to be prepared. I did a search but I can't find anything that relates to my situation. I believe my main drain runs throught the skimmer with a valve to control how much is pulled from the skimmer and how much from the main drain. From the pool, the pipe runs underground and tees into the vacuum port with a valve, then to the pump. I assume I can hook to the skimmer port and blow out the skimmer line, close off the skimmer at the valve and blow out the vacuum line, but how do I blow out the main drain and cap it off? Since the valve (Hayward SP1082GV) is taken out of the skimmer for the winter, there's no valve to close off the main drain and hold a column of water. Should I build an assembly from PVC pipe that has a valve in it for use during the winter? There's no way I could blow air into the drain and be fast enought t oplug it before it refilled with water. Since this is my first year closing, I will be hiring the local pool store to close so I don't miss something important, BUT, they also closed last year and I don't think the lines were blown out. They are a flexible black pipe that can withstand freeze (at least that's what they say). However, I'd feel better if they are blown out and will do it myself if they don't.