I use a water filter (chlorine dixide tabs as a back-up to my filter) for purification on the trail, but with winter approaching I was curious if anyone had some insight on how best to manage water purification. In subfreezing weather I have brought my filter into my sleeping bag to keep if from freezing which would render the filter useless. Tabs and other chemicals usually need the water to be at a minimum temp to be effective. Aside from boiling (that means bringing more fuel) are there any suggestions on this topic as to how to better manage water purification in extreme temps?
Pilot