Transfer Fuel to a New Canister with this Gadget

Let’s face it, most of us use canister stoves.  They’re easy and convenient—a no-fuss, no-muss—way to cook!  (what is muss anyway?)

However, one of the little situations we might not think about is that bit of fuel left in the can when we return from our latest hike. What are you going to do with that almost empty can? Do you grudgingly haul it, along with a full can, on your next trip, in hopes of using it up?

Do you put it on the shelf and watch them turn into a little collection?

Sometimes we just close our eyes and toss them in the trash. Well, there’s probably worse stuff in that landfill.

stove-refill-cans

Recently my hiking buddy, Gunny, told me about a little gadget and accompanying trick he saw on YouTube, which for the first time in a long time actually has that WOW factor.

stove-refill

This little gadget safely and easily allows me to transfer unused fuel from one can to another!

This led me to do some extensive research, because no one wants to blow themselves up in the name of backpacking experiments. I guess it’s in the nature of being a retired engineer to explore this.

Here’s how you do it.

  1. Get the G Works Gas Saver Cartridge.
  2. Have two cans, both partially or almost empty (doesn’t matter).
  3. I recommend chilling for just a bit, the can that is going to RECEIVE the fuel (call this the New Can). This lowers the vapor pressure in the can compared to the can you want to empty (Old Can) (which you want at room temperature). This just makes the fuel transfer a little easier.
  4. Make sure the valve is closed.
  5. Attach both cans to valve. The valve is ONE WAY, the direction is marked by bubbles, going from larger to smaller – this is the flow direction. You want the fuel to go from the Old Can to the New Can.
  6. The Old Can you want to empty (at room temperature) is on the valve side with the larger bubble.
  7. Open the valve. Wait a couple of minutes.
  8. Close the valve. Remove the cans.
  9. Shake the Old Can, it should have less fuel, preferably it will be empty.

stove-refil-transfer-croppedl

Et Voila! You have now emptied out your old canister and can safely dispose of it.

A Little Safety and Technical Stuff

If you have a scale for your smaller backpacking items (you should be weighing all your gear anyway!!), I suggest weighing and recording the before and after weights of both cans.

This is the best way to ensure that your fuel is going in the right direction and that you don’t overfill the new can.

PLEASE DON’T LEAVE, BUT WE NEED TO DO A TEENSY BIT OF MATH.

JUST ADDITION, I PROMISE.

I’LL MAKE IT EASY.

PLUS YOU’LL BE THE SMARTEST PERSON AROUND THE NEXT CAMPFIRE!

A very short discussion about the smaller versions of the canisters

When you buy it off the shelf the label will read something like:

3.53 oz/100g  – This is content gas weight or how much gas is in the can.  This IS NOT the total weight of the CAN + GAS.

dsc03453

CAN + GAS  = 7 oz or 198 gr

GAS (alone) = 3.53 or 100 gr.

(let’s round this stuff off and only use grams)

FULL CAN = 200 EMPTY CAN = 100

FULL CAN = 200

EMPTY CAN = 100

If you weigh your can before a hike, and it reads 150, that means you have 50 gr of fuel or about half a can.

The closer you get to 200, the fuller the can.

The closer the can is to 100, the closer to being empty.

By the way, if you read my stove article, my jetboil uses 5 gr to boil two cups of water. So a new, small can, with 100 gr of fuel, should give me 20 burns (100 divided by 5), sorry, division used there.

Ok, back to transferring the gas.

IMPORTANT SAFETY TIP

Don’t do this around open flames!

Make sure the area is well ventilated, like outside, in the backyard.

When are you filling the NEW CAN, you just don’t want it to exceed 200 – OK?  Keep it safe and maybe only fill it to 190 (gr).

Again, I demonstrate the process here.

When you finally do it, it is sooo easy!

To get comfortable with this process, try doing just a little bit at a time and weighing the cans to make sure one is getting lighter and one is getting heavier.

A note on any concerns about the valves.  This adapter is the EXACT SAME connection as your canister stove and should have no more or less effect on the valve properties.

Where does one get this valve? I found mine here.

stove-refill-valve

Next Post:  Going beyond simply emptying old cans:  refilling cans with ‘off the shelf’ fuel (as in butane cans you didn’t know were sold at your local Ace Hardware) and saving a lot of money.

 

 

 

 

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Comments 5

  • Avatar
    Brian Lewis : Apr 22nd

    What a delight — an article that conveys tangible, practical information.

    However: it seems to me that while you might bring the mass of fuel in the original can back up, you’re not bringing the pressure in the can back up. Is one in fact able to USE all of the fuel that’s restored to the can? Are there associated compromises in, perhaps required burn time as the refilled canister runs low, or … ?
    I’m not saying that all of the added fuel can’t be used — I don’t know! — just that in a canister of pressurized iso-butane, it seems logical that one wants to restore both fuel mass *and* pressure with which to push it out the stove jet and onto the dispersion plate.

    In any event, thanks for this; while I more typically use alcohol and sometimes other stove variants, I too have a small collection of partially used canisters because one generally wants to start a trip with a full canister.

    Reply
    • Avatar
      Phil (Dragin) : Apr 22nd

      Hi Brian, thanks for sharing. First I probably need to make a safety comment. The sides of all the cans warn not to refill, or bring near a flame, or use a windscreen, or use a pot with a base larger than 5.5 inches and most importantly do not expose to direct sunlight or get heated over 120F and do not store where the can can get overheated.

      That out of the way, the cans don’t need to be pressurized at the factory, the outside air temps (all the warnings) does that for us, as the can heats up, the inside gas heats up and expands, creating pressure. Too much pressure would be very bad, hence all the warning labels about not overheating the can.

      Do you remember that very very cold camping trip where you barely got a flame? That was because the can and fuel was cold and was not expanded enough to light. Do you remember that you had put the canister in your sleeping bag or coat pocket to warm it up? This caused the can to warm, the fuel to expand (creating the pressure needed) and the flame to light.

      That said, the can comes with 100gr of fuel, under no circumstances should you exceed 100gr of fuel or 200gr total can weight.

      Reply
  • Avatar
    Ron Sowers : Apr 22nd

    Great article. I’m anxious already for the next one. I’ve been refilling the same canister for nearly three years now. It’s a 230g Jetboil canister which weighs 126g empty. One 8oz / 277g butane can fills it perfectly. I’ve found a way to squeeze it beneath my counter while filling it. It takes a little over 15 minutes for it to fill so I just go off and do other things and haven’t had any problems yet. The cans seem to be very durable. I did the math on what a refill costs me and came up with 2.17 a can vs. 11.46 for a new one on Amazon.

    Reply
  • Avatar
    L. Wayne : Apr 25th

    Nice tool, I could see there being a lack of partially full cans in hiker boxes if this catches on. One issue… What kind of third year, second rate, design student uses a series of descending sized circles to indicate flow direction when an –> has been the international industry standard for more than a century? IF I bought one of these there would be a flow direction arrow scribed into the side as soon as it came out of the packaging.

    Reply
  • Avatar
    KaptainKrunch : Apr 27th

    My experience using this device for quite a while now does not align exactly to the steps you list above in the article. The valve is designed to pass liquid via pressure and gravity. The valve flows equally well in both directions (open it up and blow through it). The liquid will not flow up as indicated in your photos above, it flows down. Place the cold receive container on the bottom and the warm donor on the top. The warmer contents (liquid) will move from the higher pressure to the lower pressure environment. The large circle indicator is aligned to the purge button. Purge the air from the valve using this button prior to opening the valve to transfer contents. It will purge from the donor side.
    KaptainKrunch

    Reply

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