How do you prevent water in a hydration pack from freezing when on the slopes?

I have a friend that has the "Camelbak Thermal Control kit" and it doesn't work at all. I find that even when blowing the water back into the reservoir, there's still enough water that stays in the valve to freeze solid. Besides taking a drink every 30 seconds, what are some some tips to keep the... show more I have a friend that has the "Camelbak Thermal Control kit" and it doesn't work at all. I find that even when blowing the water back into the reservoir, there's still enough water that stays in the valve to freeze solid. Besides taking a drink every 30 seconds, what are some some tips to keep the water in the hose/ mouthpiece from freezing? Also, would anyone here recommend just bringing a water bottle in a backpack?
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