Over the years I've spent a lot of time winter camping, snowshoe tent or snow cave type stuff mostly in my younger years, and RV of some sort later on in life.
Unfortunately, in my experience finding or maintaining water in a liquid form was not something I found easy to do, with the only option I found most of the time involved utilizing some sort of heat source (Fuel) to provide water. Sometimes you can find a spring that is flowing, or get under the ice to find water. Seems you either have to keep it in a heated space taking up room you want to use for something else, or take the time, and burn the fuel to take it from frozen to flowing.
Are there any options for enclosing and heating the area with your water lines so that you can continue to use your tanks in colder weather?
