I have blown out the lines in the past but it seems that there is always a little pocket of water that persists and causes damage. Now I use the Vodka.
First I disconnect the water heater and use a short piece of extra line with a coupling at each end to bypass it altogether. Then I drain the water from the outside by removing the drain plug.
Now I disconnect the fresh water line from where it connects to the tank ahead of the pump and filter. I then use this line if it's long enough, (or put an extension on it til it is), and using the pump I pump the vodka through the system. I have my wife monitoring the faucets and shutting them off as each one starts spewing vodka. Don't forget the ice maker. I just loosen the connection where the water comes into it and wait til it drips vodka.
I then reconnect everything and I'm all set. It sounds like a lot of work, but it really isn't once you've done it and have everything the way you want it.
In the Spring I merely hook up to water and pump the lines out. Of course you could have a party with vodka coming out of each faucet.
It takes between four or five fifths to do the unit. I buy the cheapest stuff I can get as I do not intend to drink it.