How can I stop any water I’m carrying freezing?

Toni Wright, via email

Graham Thompson

GT – Trail’s technical editor for over 25 years – is our walking gear guru. The only way to stop water freezing is by insulating it against the cold. Large volumes of water freeze slower than smaller volumes. The water-filled tube of a hydration bladder will often freeze solid quite quickly, making a big bottle a better choice than a bladder in freezing temperatures. We all know our bodies get warm when we walk and our backs get sweaty while wearing a rucksack. It should come as no surprise then to learn that the best place to stow your water in your pack is as close to your back as possible, so your body heat stops it freezing. You can insulate your water container too, by placing clothing around it, such as your insulated jacket or spare fleece

(which you should always be taking on the hill in winter anyway). You can also get insulating sleeves for bottles that help to keep the contents cold or hot; or you could make your own from some old socks, some closed-cell foam matting, or household boiler or pipe insulation. If your water is starting to freeze then it’s worth tucking the bottle inside a jacket pocket so your body heat is even closer. Some mountaineering jackets have water-bottle-sized pockets on the inside to allow this. Of course a cold water bottle will drain body heat, so you’ll need to keep yourself warmer in the process to compensate for this heat loss. Using additional heat sources such as handwarmers taped to the side of a water bottle will also slow down freezing. Top tip: if you think your water is going to freeze then store it in your jacket or rucksack upside down (assuming it has a well-fitting leakproof lid!). A container of water will freeze from the top down, so once you re-invert it you will still have some unfrozen slush that you can drink via the spout.