While we’ve heard of DIY methods for transferring fuel from one isobutane canister (the ones typically used in backpacking) to another, we haven’t seen a dedicated valve designed for the purpose marketed to the outdoor world yet. Well, until recently.
Eric Flottman, an Arizona-based backpacker, was tired of the partially filled cans piling up in his garage, so he set out to design a simple, inexpensive device to fix that. It relies on simple physics to work.
When fuel is cold, it condenses. When it gets warm, it expands. To use the Flipfuel, you put the canister you want to fill (the intake) in the freezer to chill the fuel and the one you want to empty (the output) is sitting squarely in sunlight to warm the fuel.
You wait a few minutes for the temperature differential to increase, then pop the intake can out of the freezer, thread on the FlipFuel, attach the output canister, and open the valve. The warm fuel expands into the colder canister, and voila, you now have one empty can and one that’s, well, not empty.
That last bit can be a problem as you really don’t want to overfill a fuel canister. Unfortunately there’s not an easy way to tell how full a canister is. A method we like is floating the canisters in water. Some brands (MSR is one) print a small label on the canisters that show the approximate level of fuel that will be in the can when it floats at a particular level. As long as you conduct something like the float test and ensure the cans you’re filling are less than half full, you should be good to go.
Of course, then you still need to responsibly dispose of the spent canister and here’s a good primer on that.
Would be cooler if there was a way to simply refill the cans somehow, rather than have to buy new ones all the time, but this is a step in the direction of far less waste.
The device costs $35, and, conveniently, weighs 35 grams, though hard to imagine carrying one with you in the backcountry.