How to Refill 1lb Propane Bottles


How to Refill 1lb Propane Bottles

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Is it safe to Refill Small Propane Bottles?

The easy answer to the question is no.  However, with some common sense and attention to detail it is not as dangerous as some would have you believe.

However, this is the kind of post that my disclaimer was written for. If you don’t have some common sense do not try it.  So far, this small propane bottle refill article is the only project that caused a mutiny of my video crew. The wife was very unhappy about my attempts to learn how to refill 1lb propane bottles.  However, she had no real concern about it until I gave my disclaimer on the video.  After I started talking she was “What you mean this is dangerous?”

I will give you two caveats before we get started. Small propane bottles are not designed to be refilled.  Treat the refilled 1lb bottles 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.

Is it Legal to Refill 1lb Propane Bottles?

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.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.

Why Refill Small Propane Bottles?

Small one pound propane bottles are handy.  They are much easier to use than larger tanks.  Additionally 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.

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 (This site is no longer working) Tim invented a much easier process to refill these tanks and I copied it shamelessly. Please give Mr. Flanagan credit for his great work.

In a catastrophic disaster, this infrastructure may not be able to provide the bottle. I know in the recent Alabama tornadoes, 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.

Refilling Small Propane Bottles with an Adapter

The quickest method to do this is to buy a propane tank refill adapter. Mr. Heater sells them for about $12.00 on Amazon. 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 be totally aware of the dangers. Leveling your house in a huge propane fireball would not be something your insurance company, wife, or neighbors would understand.

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.”

How it Works

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.  At higher temperatures, more liquid expands causing higher pressures.

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.

If you are informed of the risks involved, and decide you are willing to take a greater risk to get a full refill, you could reduce the pressure in the cylinder by taking a pair of needle-nose pliers and pulling the pressure relief valve of the cylinder you’re refilling. This reduces the pressure and allows the liquid propane to fill the cylinder. This is pretty risky, as it not only releases some propane into the atmosphere around you, it also may overfill an empty propane cylinder.

If you are going to try this you must weight your cylinder and compare it to the weight of a new cylinder. If it weights more it is too full, and may rupture if heated (by the sun for example). Doing it this way also increases the risk for leakage, which in turn increases the risk of you turning yourself into a charcoal briquette. Personally, I omit this step.

Problems with Propane Refill Adapters

There are some problems with the propane adapters like the Mac Coupler or the Mr. Heater.  Turning the valve on the large tank when the adapter is installed is awkward.  An adapter was created to solve this problem.  Additionally, it also makes it easier to charge by adding a separate valve. A tertiary advantage is that the parts to make an adapter turned out to be slightly cheaper in my area.

Making a Better Propane Refill Adapter

You will need a ¼ brass elbows, a ¼ inch brass pipe nipple (about 6 inches long), a ¼ brass ball valve, a Mr. Heater F273756, Soft Nose POL with Hand wheel x 1/4″ male pipe thread, and a Mr. Heater F273754 1″-20 female throwaway cylinder thread x 1/4″ male pipe thread.

The Mr. Heater part F273756 screws into the propane supply tank, and into one of the brass elbows, the other end of the elbow is screwed into the pipe nipple. With the tank sitting upside down, the nipple should be pointing toward the floor. The valve screws into the pipe nipple. The Mr. Heater part F273754 then screws directly into the lower end of the valve. Check all connections for leakage and use Teflon tape.

This is one device that you do not want leaking. It is also imperative that you use brass fittings. You need to use non-sparking metals when dealing with flammable gasses.

By adding this adapter the small bottles are able to hang vertically.  The adapter length gives you plenty of room to work. The ball valve makes it easy to quickly change cylinders (without having to mess with the upside down supply tank.

I cannot stress enough that this project requires caution and uncommon sense. Propane is very hazardous if not treated with respect.  I like to think of it like eating bugs, I know I can if I need too, but it’s not something I practice a lot…




  1. Bonesmcgee
    • Scott Shannon

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