Heads up, folks! I found out the hard way to REMOVE the outdoor shower hose even after you blow air through. What can happen(and did with mine) is a bit of water, doesn't take much, will dribble back down into the mixer, freeze & crack the unit. I found the leak as I was hooking up power on our first trip of the "spring" season when water was dripping from the floor. The unit will need to be completely replaced. My dealer is helping me out, and all will be good once the replacement comes in.
So... add to the "Airblow" process...Remove flexible hose THEN blow the lines! Note to self!