James: Even if you 'blow' the lines out, there will still be some water that accumulates in the low areas of the lines -- as many have said, antifreeze run thru the pump and fill all the lines -- this takes care of getting water out of the pump (replacing it with RV antifreeze) and also puts antifreeze in those low areas of the lines. Be sure to do your outside shower (if you have one), and your washer lines if your unit is plumbed for one (some people have installed shut-offs to the washer lines at low points to keep those lines clear. Be sure and put a cup or two of antifreeze in each drain (to fill the p-trap); as for the refer -- empty it of everything and then shut it off -- be sure to put something in the doors to keep them propped open some. Otherwise, come spring you will have a nasty, moldy surprise possibly waiting for you. I know I'm forgetting something --- Oh yeah -- some people have posted that they put 'dri-rid' or something like that in the unit as well -- basically this is an air drier compound that comes in a small bucket shape -- they use it to remove the excess humidity out of the air in the closed up unit -- not sure where they were located or where you are but have read of several doing this because the unit gets a 'musty' smell to it while closed up. Ah yes - what I was forgetting -- don't forget to drain your gray and black tanks!!! We used our trailer last December and when we got back home it was cold and snowing -- I winterized the lines but said I'd drain the tanks on Saturday which was supposed to be warmer. I forgot. Needless to say, come March I had one very putrid mess to correct.......
... drain them, flush them, and put drain that as well. The little antifreeze that gets into them from filling the traps is not nearly enough to keep those tanks winterized if not drained first.
Sorry for the long post but hope I've helped.
Hope all this helps.