Originally published at Notes from the bunker…. You can comment here or there.

Someone asked in comments how to keep water from freezing in BOBs in this cold climate. Valid question. I’ll expand on it a bit further.

Obviously, if youre going to leave a pack in the truck when the outside temperature is below freezing whatever is in that pack is going to freeze. Since water is a staple emergency item to keep in the truck, it stands to reason that youre going to have some problems when the temperature gets below zero.

Normally, I keep a five-gallon jerry can of water in the back of the truck. In winter it freezes into a solid block of ice, which makes it fairly useless. The solution to the problem of water freezing is not in how to avoid the situation, because you really efficiently cannot, but how to deal with the situation. The simple answer is: you thaw your frozen water. Obviously the smaller the frozen water supply, the faster it will thaw. Lets say you have a liter bottle of ice, and you have a bunch of ice cubes that, when melted, equal one liter. Spread your ice cubes out, and lay your frozen one liter water bottle next to them. Which one is going to melt first? The smaller ice cubes, of course. The smaller the package of water the faster it will freeze, but it will also thaw faster.

In the winter, I like the foil pouches of emergency drinking water. They’re compact, easy to distribute in a full pack, and if you stick one in a pocket it will thaw very, very quickly. Each one is around 4 oz. so a dozen or so scattered amongst your gear gives you a good supply of water and if they freeze you’re not going to have any trouble at all thawing them in a hurry with anything other than simple body heat.

Plastic bottles seem to hold up very well to repeated freezing/thawing cycles. Several brands of bottled water are available in ‘hand grenade sized’ bottles that should thaw significantly faster than a 20 oz. bottle. To play it safe, I usually keep the water bottles in a ziploc bag or two just in case things do explode from the cold. As long as a Nalgene bottle is not filled to the brim, it seems impervious to freeze/thaw cycles.

When out in the field I usually use a CamelBack-type hydration system. I carry the water reservoir inside my pack, closest to my back. Freezing is never an issue, the body heat transmits through the pack into the Camelback and keeps things warm enough, along with the constant motion, to keep things from freezing. What about the water in the drinking tube? Easy – when youre done drinking, blow into the tube and force the water back into the reservoir so there is nothing but air in the tube. No problem.