Steve, very good points! To prevent freezing of the tube, I just unscrew the faucet attachment -- the tube drains immediately. Some heat is lost through the tube, but not enough to merit insulation. The foam blocks that I have inserted into the outdoor shower box greatly reduce the heat loss from inside the trailer. And yes, we do have to be mindful of the water heater vent and the furnace vent, both of which are near the tube. There is about a four inch gap between the vents and the tubing -- I probably should run those appliances to see if the tube gets too hot.
