I am in North Jersey and the winters are cold with snow. I am in the middle of switching pool service companies. The current company drains the raised spill over spa nearly all the way down and blows out the lines, etc. The same hardcover used during the summer is reused. The 'new' company mentioned there should water left in the spa to prevent it from "popping" out. He also mentioned a separate cover but I need additional details. I've read several threads on the forum where some completely drain and some keep water. Is there pro/cons of each approach?