Considering your northern location, I would have shut off valves inside the house and make provisions the drain the supply lines before freezing weather. If you can't get a natural slope drain the water, then you will have to use an air compressor to blow the water out. You could have difficulty getting really hot water if there is a very long run outside, so insulate the hot water line well. The drain must be trapped just the same as one inside, but I would just remove the trap when the water is drained in the fall. Sure, you could use RV antifreeze, but it will be much cheaper and quite easy just to remove the trap.