I’ve written before about refilling disposable one-pound propane cylinders that so many portable appliances use. That article is the most-viewed post on Navagear.com. It’s popular because the subject is relevant to a wide variety of outdoor recreational enthusiasts: backpackers, kayakers, hunters, boaters, you name it.

I’ve been refilling these handy green propane bottles without mishap for a couple years now. Recently I’ve assembled a much-improved refill adapter. I’m going to describe the refilling process in detail.

First, though, it’s necessary to protect myself with disclaimers andcaveats refillors. Let’s keep it simple, shall we?

Under no circumstances should anyone ever refill disposable propane cylinders using the following method.

Find a well-ventilated area, outdoors, away from all sources of heat, flame, and sparks. Ditch the cell phone.

Assemble your tools: a propane refill adapter, a pair of needle-nosed pliers, and a pair of medium-thick work gloves.

Take a standard 20-pound propane cylinder—the kind you see attached beneath barbecues—and turn it upside down on a table or platform of some kind.

Screw your refill adapter to the OPD valve of your propane cylinder. This is a left-hand threading, so you need to twist the adapter counter-clockwise to tighten it. Ignore the naysayers who warn that modern cylinders with OPD valves won’t permit liquid propane to be extracted using this method; it works just fine.

Screw your empty disposable propane bottle onto the refill adapter. Be careful here, since the bottle’s threads are right-hand, and the adapter-to-OPD threads are left-hand; tightening one loosens the other. Hold the adapter firmly while you tighten the bottle.

Open the valve on the big supply cylinder. You will hear the propane moving from the large container into the smaller one. Gradually, the movement will slow down until you can no longer hear it.

But the cylinder isn’t yet full. You need to reduce the pressure in the green cylinder to allow more liquid propane to enter. The easiest way to do this is to put on your gloves and use your needle-nose pliers to pull up on the pin of the relief valve in the green cylinder.

This will release some propane (gas) into the atmosphere. Obviously, this isn’t ideal, and it doesn’t smell good, but I’ve not had good luck with other methods of creating a pressure differential between the cylinders.

You’ll only release a small amount of propane. Still, that gas comes out cold, and liquid propane may sputter and squirt out, which is even colder. Seriously, it’s freezing cold. It may seem ironic that one of the most likely causes of injury while refilling fuel cylinders is frostbite, but that’s the way it is. Always wear your gloves.

Once you think the propane cylinder is really full, close the valve from the supply tank and (still wearing gloves) unscrew the green can from the adapter. Weigh it on a postal or kitchen scale capable of showing you ounces, or tenths of ounces. The tare (empty) weight of Coleman green propane cylinder is right around 13.6 ounces. Full, it should weigh 13.6 ounces tare plus 16.4 ounces of fuel, for a total of 30 ounces, or one pound, 14 ounces. Don’t worry if you’re an ounce or two shy. It’s pretty difficult to get these cylinders full without going over. If you’re over, you need to remove some propane; either attach it to an appliance and use some right away, or pull the pin on the relief valve to release propane gas into the air.

Before you attach the cylinder to an appliance or introduce any source of flame, spark, or ignition, check to make sure your refilled cylinder isn’t leaking. Initially, you can listen for hissing. If you hear any, it’s leaking pretty fast. The most frequent source of leaking is the relief valve. Take your pliers (gloves on), lift the pin, and let it snap back. Often, this will be enough to seat the valve properly. Listen again.

If you don’t hear anything, introduce a little bit of soapy water onto both the relief valve and the primary valve. You’re looking for bubbles. Bubbles are bad. If you get bubbles at the relief valve, try to reseat the valve again, add a little more soapy water, and test again. If you can’t get the leaking to stop, you may need to retire the bottle. Unless you have a way to recover the liquid propane in this bottle, you’ll just have to leave it outside in a well-ventilated area free from sources of ignition and let it drain.

Let me repeat: No one should ever refill disposable propane cylinders using this or any other method.

Nevertheless, that’s how I refill disposable propane cylinders. The commercially available refill adapters are hard to use. They fall short in three areas. Because you need to place your pliers inside the guard ring on the supply tank, it’s difficult to reach the relief valve.

Additionally, you have no control over the location of the relief valve, and if it ends up beneath the fill valve once it’s screwed on tight, you can’t fill the cylinder fully; pulling the pin on the relief valve just releases liquid propane, not gas propane.

Finally, it’s awkward to tighten-up the conventional in-line adapter due to the left-hand/right-hand thread combination. And it’s awkward to reach the OPD valve on the supply tank, which becomes a nuisance if you’re refilling several cylinders.

I’ve fabricated my own, much-improved refill adapter, using off-the shelf plumbing components, which addresses all the shortcomings.

The elbow allows the green bottle to sit vertically, and eliminates the problem of tightening both the left-hand threaded supply-tank connection and the right-hand threads on the disposable bottle. The six-inch pipe gives me plenty of room to reach the relief valve with the pliers, regardless of the valve’s final orientation. The ball valve allows me to quickly change tanks, or remove a tank briefly to weigh it, without having to manipulate the supply tank’s OPD valve every single time. Oh, and it’s a lot easier to reach the OPD valve with the new adapter, too.

I would normally close a how-to piece with something akin to “good luck!” But in this case, I better just remind you never to do as I have done. Be safe.