Solar Bag Purifies Snow for Drinking

Sure, Dad always warned you not to eat the yellow snow when you were a kid, but even the pretty white stuff can harbor some nasties. Yet, for individuals traversing the back-country in the winter–such as cross-country skiers, first-responders and avalanche rescue crews–melting snow for drinking water is an ideal, if time-consuming, way to avoid carrying around a lot of bulk in the form of liquids. William VanZee of Brooklyn, New York, has conceived of a safe, fast snow-drinking solution: the Pure Melt Bag.

This device consists of a waterproof, roll-top interior bag–similar to the dry-bags used on river expeditions–which fits inside a backpack shell equipped with a solar heating element and a charcoal filter. Simply stuff the interior back full of snow, roll the top down into the secure position, place it in the back-pack shell and away you go along the trail. As you move, solar energy gained from the sun on your back heats up the wire element, melting the snow. On its way down to the tap at the bottom of the backpack, the water passes through a charcoal filter, removing impurities.

Pure Melt Bag

image via William VanZee

The Pure Melt Bag can be used by itself or strapped on the outside of a larger backpack; it features a removable nozzle and charcoal filters (which must be changed out according to manufacturer instructions in order to maintain the bag’s purifying functions).

Pure Melt design

image via William VanZee

This seems like a great concept for those who spend a lot of time hiking in the winter–for those of us who just frolic in the white stuff now and then, probably, not so much.

Susan DeFreitas has covered all manner of green technology for EarthTechling since 2009. She is a graduate of Prescott College for the Liberal Arts and the Environment, and has a background in marketing green businesses. Her work on green living has been featured in Yes! Magazine, the Utne Reader and Natural Home.


  • Reply March 17, 2011


    This seems entirely useless. The article itself points out that carrying around liquid is inefficient and generally avoided by anyone in the back country – yet you need to carry around the snow until it melts into water using this device. Anyone out in the snow overnight packs a camp stove that will melt water with lightweight fuel in a very short amount of time. Not to mention the fact that where there’s snow worth hiking for (read: POWDER) it usually means clouds – would anyone want to literally put their lives on the line hopeing for sun to melt their drinking water?

    I’m sorry, great attempt, but this is a big flop.

    • Reply March 22, 2011

      William Van Zee

      Hey Max,

      I appreciate your skepticism, as I myself did quite a lot of questioning during the design process of the Pure Melt bag. I urge you to check out more of the development of the bag on my coroflot:, but to cover some of your critiques: The bag does not require the user to carry the water and can be easily strapped to a tree at your base camp to produce drinking water while you focus on other aspects of survival. The concept was to create a lightweight- highly portable system that rather than replacing the standard gas-boiling technique, could supplement your use of fuel- allowing you to conserve for real emergencies and save packing space for things like food and clothing. In addition, the recent advancements of solar technologies has resulted in numerous rigid and flexible solar-cells that are efficient at converting solar energy even in very low light environments.

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