Bob,
If your coach has an Aqua Hot, I would caution you on just using compressed air to blow out water lines. The Aqua Hot has a system of copper coils which contain water at the bottom of the coils, that no air pressure can reach. There is a definite possibility of a leak from frozen lines. A lot more than $96 to repair.
To winterize those coils, you have to pump the pink stuff in to them. I have a system that allows me to winterize the entire coach in about 15 minutes for the cost of 3 or 4 gallons of the pink stuff.
1. Go to any hardware store and buy a 36 or 48 inch water line for a washing machine. They look like braided tubing with a connection on each end.
2. Disconnect the inlet hose to your water pump. Connect the braided line to the inlet. One of the ends is an exact match for the threads.
3. Have a partner (we use walkie talkies) in the coach, while you dip the other end of your braided line in to a bottle of the pink stuff. Have a prearranged signal for GO and STOP. On GO have your partner open the hot water faucet in the kitchen sink (we always do that one first because its the farthest from the water pump, and will take the most pink stuff) The pump will suck the pink stuff out of the jug quickly, so be ready for STOP so you can change jugs. Your partner should turn from hot to cold as soon as pink stuff starts coming out of the faucet. Do this for each water source in the coach. First hot, then cold. Don't forget the toilet. When you are done, the pink stuff will be pumped through the Aqua Hot, thus winterizing it.
4. You could just dump the jugs of pink stuff in to a 5 gallon bucket to eliminate having to change jugs mid-operation. Whatever works for you.
5. Use the leftover pink stuff to winterize your washing machine. The instructions are in the owner's manual. Takes 3 minutes.
6. Reconnect your water pump. Easy cheezy.
7. We live in a cold weather climate, and I have used this method on our Beaver for 8 years. Never any problems.