How to Refill Small Propane Bottles

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Alright, this is the kind of post that my disclaimer was written for. As a matter of fact, this was (so far) the only project that almost caused a mutiny of my video crew — The wife was very unhappy about this project.
Small one pound propane bottles are handy; they power many things, and are cheap. The problem is that they are disposable, and that you need to have infrastructure in place to keep creating them. In a catastrophic disaster, this infrastructure may not be able to provide the bottle. I know in the recent Alabama tornados, many stores were unable to provide needed supplies, and that many people had to subsist on what they had in their homes prior to the storms.
I have been working more lately with using flammable gas a fuel source, and find propane to be very useful. Unlike liquid gasoline it does not go bad. It’s safer, and MUCH easier to store than gasoline. The benefits of propane and the ease of using small bottles found me wanting to find a way to refill those small cylinders from my bigger tank. I quickly found both an adapter do this, as well as an awesome idea from Tim Flanagan of Tim invented a much easier process to refill these tanks and I copied it shamelessly. Please give Mr. Flanagan credit for his great work.
Now before we get started in the how to — I must give you two caveats. These are not designed to be refilled, so it is dangerous — Treat the refilled tanks as if they may leak at ANY time. This means store them outside and away from flammables. Liquid propane has a 270 to 1 expansion factor which means 1 gallon of confined liquid will expand to fill 270 gallons of air. If a 10 gallon LPG tank was to leak and find an ignition source — well, 2700 gallons of propane exploding would cause a BAD DAY. If you don’t believe me please learn about the Waverly Explosion.
The second caveat is that this may be illegal. These cylinders are not DOT-approved for refilling. Refilled cylinders can’t be sold or transported commercially. However in my totally non-lawyer PERSONAL opinion (meaning what I believe, which is different from me telling you I think it is legal for you to do), is that I can do it myself for my use at my home without causing a SWAT raid.
The quickest method to do this is to buy a propane tank refill adaptor. Mr. Heater sells them for about $20.00. You can also buy a similar product called a Mac Coupler. Either way, you need to understand how propane works before you attempt this.
Obviously anytime you’re working with pressurized flammable gas you need to crack a book and be totally aware of the dangers and precautions. Leveling your house in a huge propane fireball would not be something your insurance company, wife, or neighbors would understand (not that it would matter, as you would be a charred mass of pink mist.)
At normal atmospheric pressure and temperature, propane is a gas. This gas is heavier than air, so it will want to settle and collect in low spots. It is absolutely essential to store this outside so that any leaks can dissipate. Otherwise you risk blowing yourself up when you turn on a light or your AC kicks on.
Mr. Flanagan said it best in his article “The propane we purchase is “”Liquefied Propane Gas”" (LPG), which has been compressed into a liquid and is stored in cylinders designed to keep the propane compressed. The propane is always under pressure, and will tend to escape if you let it. So the integrity of your storage cylinder is another extremely important safety factor. Don’t skimp. I don’t know what the lifespan of refilled “”disposable”" cylinders is, but if they leak or they’re visibly damaged, it’s time to get rid of them.”
Due to the physical properties of the propane, the pressure will remain constant in a tank no matter what the size of the tank is. As long as some liquid propane remains in the tank to vaporize, whether it’s full or almost empty the pressure inside the cylinder remains constant. That’s why you can cook just as well with a nearly-empty tank as with a full tank. The only thing that changes the internal pressure is the temperature. The higher the temperature of the liquid propane, the more gas is formed which can significantly increase the pressure inside the tank.
The idea in refilling a tank is to move LIQUID propane into the empty cylinder. It does no good to move GAS into the cylinder. The heavier liquid sits at the bottom of a cylinder, and the lighter gas sits at the top.
Because of this you turn the supply tank upside down so the valve is on the bottom, and the smaller tank is lower than the big tank. This allows the pressure of the propane gas to push liquid propane into your receiving tank rather than the just the gas you would get if the receiving tank was higher than the supply tank….

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