[Daryles]

I agree with Dutchman.
Murphys law will take over while you are gone.
I use my tire air compressor and an adapter on the City water port to blow out my lines.
I leave the water heater bypas in normal flow.
Open the freshwater tank drain and the low point drains. Open a faucet inside for air. Turn OFF your water heater circuit breaker. Remove the anode Ron and let the water heater drain.
Put the anode back in. Close the drain ports and start your compressor. Set it to 55psi (same pressure as your water pump works).
The water heater will act like an accumulator for the air compressor.
Open and close each faucet one at a time starting
With the outside shower. Don't forget the winterizing port. Blow air through it too.
Now go inside ond do each faucet and toilet flush.
Cycle each faucet several times.
Don't forget to do the washing machine pipes. You will need a hose to connect to them to catch the water.
Keep your heat running.
Make sure you have TWO full propane tanks.
Leave both valves turned on. Your auto switch over valve will switch to the other tank when one is empty. You will go through a lot of propane at those temperatures.
Good luck