If you use a canister backpacking stove like a Jetboil Flash or an MSR Pocket Rocket, you probably have a lot of partially used isobutane canisters in your gear closet. While the ease of using canister gas stoves has revolutionized backcountry cooking, it also creates a lot of waste since there’s no convenient way to use up all the leftover gas in a canister or to combine two partially filled canisters to make a whole one.
That’s why the G-Works Gas Saver caught my eye. It’s a two-way isobutane canister adapter that lets you transfer the gas from one isobutane canister to another so you can refill partially used or empty canisters.
Made in Korea, you can buy the G-Works Gas Saver on Amazon. Be forewarned: it doesn’t come with any instructions at all, which is a little concerning since it’s used to transfer highly flammable materials that can cause serious injury or burn down your house (see disclaimer below). And while the G-Works Gas saver does make it possible to transfer gas between canisters, I suggest you use an inverted canister stove like the Kovea Spider or the Jetboil Joule, not an upright one, to burn gas that’s been transferred to another canister. More on this below.
How It Works
The G-Works Gas Saver plugs into gas canisters using what called a Lindal valve. This is a standard canister attachment system that is used universally on canister stoves (in the US, but not Europe) to ensure that canisters from different manufacturers can interoperate with other manufacturers’ stoves. For example, it’s the reason you can use Jetboil, MSR, or Primus isobutane fuel canisters with a Snow Peak canister stove.
The G-Works Gas Saver has two Lindal valves that you screw onto the canisters and a twist valve that controls the flow of gas from one canister to another. When transferring gas, you want to have it flow from the higher pressure canister to the lower pressure canister. One way to achieve this is to stack a fairly full canister over an empty canister (the full canister is under higher pressure than the empty one), so the fuel drains to the lower canister.
You can also raise the pressure inside the upper canister, by raising its temperature. For example, plunge the upper canister into a bowl of hot water for a few minutes before attaching it to the Gas Saver. This is useful to speed things up and when the bottom canister has more gas in it than an upper, mostly drained canister. The actual speed of the transfer depends on the amount of the pressure gradient, but figure about 15-20 minutes to fill a small empty canister from a large, mostly full canister. The process is not terribly fast.
While can overfill the bottom canister beyond the amount of fuel that it originally held, I’d advise against doing this for safety reasons. You can measure the amount of fuel transferred by weighing the canister before and during the process so you know when to stop.
For example, if you know you have an empty canister, search for its net weight, which is usually printed on canister’s exterior. If a canister has a net weight of 110 grams, this tells you it had 110 grams of fuel in it when you bought it new. When refilling it, stop when its empty weight has increased by 110 grams. It helps to have a scale handy for this process.
What Gets Transferred?
Good question. It’s hard to know exactly what kind of gas is being transferred from one canister to another since different canister manufacturers mix butane, isobutane, and propane in different combinations to improve cold weather performance. Things get even more uncertain when you mix one manufacturers fuel into another. Do the constituent components stay “mixed” or do they separate when transferred using gravity. For example, would the heaviest fuel component drain from the top canister into the bottom canister first before the lighter components?
What I’ve found by burning the transferred gas on different stove types is that I get 15-20 minutes of burn time when using an upright canister stove, after which the force of the flame weakens considerably or putters out completely, even though there is plenty of liquid fuel left in the recharged canister. This happens even after I’ve let the canister rewarm to outside air temperature between long burns, but the flame never returns to full power in an upright stove after it begins to falter.
But if I invert the recharged canister and plug it into an inverted canister stove, like the Kovea Spider, which burns unvaporized liquid fuel, I can get another 20-30 minutes of burn time from the canister until it’s completely empty.
I’ve seen this happen before with canister stoves, when the fuel component inside the canister that is responsible for vaporization in an upright stove burns off (propane) leaving the liquid component (isobutane) behind. Hik’in Jim (Adventures in Stoving) has an excellent article that explains canister gas blends, vaporization, and cold weather performance that it worth reading if you want to dig into the details.
Use with Inverted Canister Stoves
Based on my testing, my advice would be to only use an inverted canister stove with refilled canisters to ensure that you can use all of the gas in the canister. The Kovea Spider can burn fuel from a canister oriented in either direction. I think inverted canister stoves like it are the best way to ensure you can use the entire canister contents when camping with refilled fuel canisters.
Is the G Works Gas Saver worth buying? While it provides a way to transfer unused gas between canisters, it takes a fair amount of time and fiddling to get the job done. I honestly can’t see this becoming a big consumer hit and I doubt any of the existing canister or stove manufacturers will champion it, though time will tell. While the G Works Gas saver does reduce canister waste, there are easier ways to accomplish this by switching to another backpacking fuel source such as alcohol, white gas, wood, or esbit cubes, which are unencumbered by fixed size containers.
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