You can't blow the water out of a LG heater. IF you try, you will only remove the water from the top 2-3 inches at best.
Waldo, I figured out damn quickly that draining the heater is a foolproof way of keeping it from freezing.
My van needs to be insulated. The damned thing was set up for Las Vegas weather, not middle of nowhere in Nebraska weather. For that matter, I need to replace the van with one that has a gas engine! Stupid Diesel is about 90 cents higher than regular unleaded here, and the diesel doesn't like to start very well when it is cold out (and I do have an engine block heater)