I drain all the water and empty the water heater and filter. Then used compressed air at 40 psig into the city water connection. Purging the water heater first, then sealing it and do all the toilet supply, shower, faucets hot and cold. Bypass the water heater, then suck up some RV antifreeze with the pump and run it through the lines. Then blow those lines clean again. Finally pour some antifreeze straight into the drains to fill the traps and leave some in the toilet bowl.
I also blow the tank fill for just a little to make sure no water is left in the fill line.
2009 Georgetown 350TS (bunks)
400W solar, 440AH 6V GC2
2009 Ford Edge AWD Ltd towed
2011 Honda Fit Sport towed