Introduction: How to Completely Refill a 1lb "disposable" Propane Bottle

Picture of How to Completely Refill a 1lb "disposable" Propane Bottle

Summer Is here and its time to go camping! I go through a lot of the small 1lb cylinders of propane. They are used for my stove, Lanterns, Heaters, etc. At  $3 to $4 a Piece, they really start to add up, not to mention that when you are done with them, they are then thrown into a landfill. No more! for about $30 you can build a refill station and refill those bottles completely for about 50 cents a bottle!

I know what you are thinking, why build this when you can buy a refill adapter ready made for your tank. I used to use one, but you can only fill your bottles about 2/3rds full. This method allows you to completely fill a bottle. much the same way as they were originally filled in the factory. and with the quarter turn valve, the refill process is quick and easy.

Disclaimer: this is the way I refill cylinders. I do not claim to be an expert, and I take no liability for mistakes you make. BE SURE TO DO THIS OUTSIDE preferably with a bit of a breeze and no near, flames, sparks, cinders, etc. Propane is highly flammable and this can be dangerous if you don't use common sense. If you blow yourself up, don't blame me!

Step 1: The Anatomy of a 1lb Cylinder

Picture of The Anatomy of a 1lb Cylinder

A 1lb Cylinder has a pressure relief valve. This is a safety feature that will vent excess pressure from a bottle. This is also used to vent the gas during the filling of the bottle. It looks much like a valve from a tire.

Step 2: The Valve

Picture of The Valve

The valve Consists of the appropriate propane connectors, a 1/4 turn valve and a street elbow to angle the bottle appropriately. I found all my parts at my local hardware store. I am sure they can be ordered on line as well.

Step 3: The Vent Tool

Picture of The Vent Tool

I no longer use the tire valve tool to vent the small tank. It is safer to use a needle-nose pliers to pull up the vent valve. The pressure relief valve is set at the factory. (as mentioned in some comments below.) it is difficult to get this back into the same setting and can lead to preventing the safety valve from working. the following is a link that I have since found that demonstrates the refill process with needle-nose pliers. (And yes it can be accomplished with a Harbor Freight valve adapter, but it is much easier to use an angled setup with more room.)

Step 4:

Picture of

Attach the Valve that we have built to a 5 gallon propane tank. Close the quarter turn valve and open the tank valve. Then invert the entire setup.

Step 5:

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Attach the 1lb Cylinder to the valve and then open the quarter turn valve. You should here propane rushing in to the bottle. Due to the fact that we have the 5 gallon tank inverted, we are pushing liquid in to the 1lb cylinder. Insert the tire valve tool into the relief valve, unscrew the valve until you hear propane escaping past the valve. I have found the most efficient method is to crack the valve open for  a few seconds and then close it. every time you do this, you will hear more liquid propane rushing in to the cylinder.

Step 6: Completely Fill the Cylinder!

Picture of Completely Fill the Cylinder!

Continue Venting the gas from the bottle in this manor until you get a small liquid spray out the vent. Once this happens, the cylinder is completely full.  Screw the relief valve closed until you hear it click. Turn off the quarter turn valve, and remove your completely refilled Cylinder! a full 5 gallon propane bottle will fill about 20 1 lb cylinders.

When I am done, I cover the top of the 1lb cylinder  with a bit of foil or plastic wrap to keep the connector clean and to mark the cylinder as full. If you save the plastic connector cap that came with the bottle, that is even better. IF you need more bottles, check the dumpster at the camp ground, there is always a plethera of them discarded by people who do not reuse...

You can now save money, and keep the cylinders out of the land fill.  Keep your cylinders dry and clean. replace the cylinder if it gets rusty or starts to leak. When in doubt, error on the side of caution.


charliewinters (author)2014-08-26

I was pretty interested in this instructable until I started reading
the comments. I found the barbed comments between you guys to be
off-putting, and will look for another source of information on this

Food for thought... If you have a pissing contest,
and fill your thread with barbed comments, you're likely to lose your
potential audience. I'm disappointed that I wasted as much time as I
did reading comments that had little to no informational value to them.

Have a nice day, and thanks for the Instructable.

weedyard (author)charliewinters2017-10-26

Real information ALWAYS includes involved discussion, and when someone puts out faulty information in the name of 'safety', (or, alternatively, truly unsafe information), they need to be called on it.

So, you are interested, and liked the information, but a little heated dicussion runs you off?

Yolorenzowhatup (author)2017-10-18

i want to do it for camping instead of just buying new packs tho

Yolorenzowhatup (author)2017-10-18

where do i get the parts at or get the deal

JudyM127 (author)2017-10-10

Great information, thanks. Other sites suggest putting the small cylinder in the fridge or freezer for 15 minutes before filling, this seems to work, along with the other sites I found your post very helpfull thanks for taking the time and effort.

SHOE0007 (author)2017-05-04

You do know in Canada in Ontario and Quebec it is Illegal to do this. You could get a half a million dollar fine and/ or 5 years (min) in Jail for attempting this.

bensteinsmoonie (author)SHOE00072017-10-04

Wow. How much if I just snort some?

Cape Charles (author)2017-09-21

Often the fill valve leaks after filling and within a few days the tank is empty.

I have tried putting a bit of WD40 on the valve, but don't know if that works.

Comments or suggestions?

Cape Charles (author)2017-09-21

Often, maybe even usually, the filler valve on the small tank leaks, and within a few days it is empty.

I have tried spraying a bit of WD40 on the valve prior to filling, but don't really know if that works.

Any thoughts or suggestions?

dhaider1 (author)2017-09-13

This would work great, but what about the safety shutoff that stops the flow should the tank be put on its side or inverted? Just for educational purposes, the vapor pressure of propane is 100 psi. just a fyi. you know the same pressure a pnumatic nailer uses.

GeeDeeKay (author)2012-07-19

While this works -- I have one of these adapters myself -- it is very important to understand that any propane canister is only as good as its hydrostatic test results. This method should have significant safety warnings attached beyond "don't blow yourself up." Ignition during the transfer process is only one concern. If the receiving canister is somehow weakened by age or handling, it could explode unexpectedly with catastrophic results.

My local gas dealer will always check the hydrostatic test date on my 20# grill tank before refilling, and if there's any question, they will not refill the tank. They're the experts so I respect their professional opinion. I go and swap the tank out for a new one at my local orange or blue mega-store.

Pressurized, flammable gas is nothing to fool around with, and any time one refills a container under pressure without a way to measure the resulting pressure of the container, especially in reference to its maximum safe internal pressure, could create a massive safety hazard.

Yes, perform this at your own risk, but understand that the larger tank could impart a significant amount of pressure on the smaller one, beyond its capacity. This could create a timebomb in a 1-lb propane canister.

shascho (author)GeeDeeKay2013-10-30

This is incorrect.
A bulk tank does not have greater pressure than a 1lb canister,
and can not possibly impart excessive pressure to it.
Also, your local gas dealer is *not* an "expert"
but simply obeys the law which mandates the expiry date for any inspection.
Checking that date gives him no information
regarding possible handling damage, etc.
Safety is Priority One,
but ignorance is a poor guide.

GeeDeeKay (author)shascho2013-10-30

I appreciate the care with which you crafted your response. You clearly know lots about me from a few paragraphs. I especially liked the part where you called me ignorant...

I'm afraid you missed the point of my comment: to try to impress upon readers the idea that this is potentially a very dangerous process. The fact that my local gas dealer actually follows the law makes them far more expert than most. They do also inspect the condition of the container and will not refill a tank with visible condition issues. Forgive me for not making clear that the "any question" reference could also include a condition check.

I've seen the 1-lb tanks take more fuel from a 20-lb tank than they are rated to hold, so perhaps I used a term that's not scientifically precise, but my goal here is to use terms that get the point across rather than precise use of scientific jargon that could cause confusion.

Sometimes an idea is conveyed more effectively with simpler words.

Lighten up, and next time try to provide criticism that's more constructive than negative.

Safety third!

shascho (author)GeeDeeKay2013-10-30

"Ignorant" is not an insult,
but rather "a descriptive term that gets the point across."
Please don't blame people for reading the words you post
rather than the meaning which you fail to state.

Ideas tend to be conveyed by accurate words.
It's difficult to correct incorrect information without using negatives.
Don't be defensive, and next time post accurate information.

Safety first!

GeeDeeKay (author)shascho2013-10-30

Well, I'm pretty sure you intended it as an insult, but it seems you preferred the way I phrased it instead. I'll take that as a backhanded compliment. It's curious that nobody else in 15 months found my comment to be so egregious to warrant a correction until your castigation finally set me straight.

The meaning isn't just in the words themselves but in the spirit of the message, as well. It's absolutely possible to address what you perceive to be inaccuracies without being negative, but only if you choose to do so. Going negative is the cheap & easy path, but it's more of a challenge and ultimately more satisfying to be supportive and constructive. I'm satisfied, you just seem negative.

I'm trying to be nice, but you're not making it easy. So, good luck with your precision issues. I'm not sure why you decided this was a battle you wanted to fight, but this isn't the hill I choose to die on, so it's all yours. Enjoy your pyrrhic victory.

And I really did mean safety third. Look it up...

BarryE5 (author)GeeDeeKay2015-11-21

I might point out that ignorance is a lack of knowledge or imformation and stupid is an inability to comprehend. Therefore there its not an insult to point out thatbthat someone is ignorant, as we are all ignorant about something.

shascho (author)BarryE52017-09-12


Paulzinemark (author)BarryE52017-09-11

You nailed it Barry!

Paulzinemark (author)GeeDeeKay2017-09-11

Gotta say, you put an awful lot of effort and vocabulary into what amounts to nothing more than a pseudo-intellectual method for being even more negative, and more insulting, than you feel he was to you. Im with him here, big words dont make you smarter or safer on most jobsites, the right words, and people that know the terms involved, do create safe practices. Rules and policies are, far too often, nothing more than a way to avoid liability in lieu of actual safety.

jtrzaska (author)GeeDeeKay2014-06-25


Aside from the exchange between you and shascho, I am grateful for your reference to Safety Third! It made me look it up, and I am glad I did. For anyone else who would like to read it direct from the source, here is a link to a letter about it by the man himself, Mike Rowe:

shascho (author)GeeDeeKay2013-10-30

Alrighty thn, GDK.
If you choose to interpret my words
in ways that I have explicitly denied,
that's your choice and out of my hands.
Seems like a lot of writing for such a trivial offence,
but it's as big as you want to make it, I guess.

I stand by my corrections.
You stated that
"the larger tank could impart a significant amount of pressure on the smaller one, beyond its capacity."
but this is simply not the case.
Cylinder pressure does *not* increase with size.

If you choose to criticise an instructable
you should first make sure your criticisms are accurate.

Safety First, and peace out!

Paulzinemark (author)GeeDeeKay2017-09-11

Not sure he called you ignorant in his post, looks like he merely was noting that ignorance really is a poor guide. You, though, double down, and claim to KNOW that a 1lb. Cylinder was over capacity? How? As stated, tank to tank, this is literally impossible, barring, as i stated, manipulation of the safety valve itself, and even then, the tanks will be of (equal) pressure, within ratings for both tanks, though the 1lb tank may be past its expansion room limit by liguid volume.

Paulzinemark (author)shascho2017-09-11

About time someone else posted this. Never once had a gas supplier employee actuall "safety check", or reject, an obviously ancient cylinder, regardless of size. It is nearly always nothing more than a liability/compliance matter or the famous "leak test" to increase revenue.

RobertJ26 (author)shascho2015-08-27

Correct:The only thing you could possibly do is if you vented it and filled it all the way to the top and warm temps expanded gasses to the point of the relief valve purging.

RobertJ26 (author)shascho2015-08-27

I believe after filling many squat tanks it's not possible to overfill unless you vented at the relief valve.I always end up with 2/3 of a bottle (chilled squat bottle) Gas liquifies in the chilled squat bottle I assume.Correct me if I'm wrong.

Paulzinemark (author)GeeDeeKay2017-09-11

The larger tank in fact holds propane at EXACTLY the same pressure. No more, no less, within an industry wide margin of error. Thus, a 100lb. Cylinder is incapable of overpressurizing the 1lb. Cylinder. It is possible to overfill, and the practice of opening the relief valve is the cause of overfilling, as it releases the remaining vapor in an "empty", allowing more space for the (same pressure) liquid displacing it. Just ignore all advice to vent vapors and you will always be fine assuming a good cylinder. Hope that helps.

KerryF14 (author)2016-02-08

Besides being very dangerous, what you all are doing is not legal. These cylinders are just that disposable. The U.S. Department of Transportation and your local building codes to some extent do not allow the refilling of these cylinders. READ THE LABEL. There are REFILLABLE cylinders that are available and safe. Manchester Tank makes one. Don't take take a chance on severely injuring yourself.

Paulzinemark (author)KerryF142017-09-11

Illegal to transport, not illegal to fill.

HWACK (author)2017-09-06


BEWARE!!!!!!!!!!!!!!!, REGARDS

thedustycelt (author)HWACK2017-09-07

Thanks for the heads up... the link used to go to a different site... I have removed it.

thedustycelt (author)2017-09-07

I no longer use the tire valve tool to vent the small tank. It is safer to use a needle-nose pliers to pull up the vent valve. The pressure relief valve is set at the factory. (as mentioned in some comments below.) it is difficult to get this back into the same setting and can lead to preventing the safety valve from working. the following is a link that I have since found that demonstrates the refill process with needle-nose pliers. (And yes it can be accomplished with a Harbor Freight valve adapter, but it is much easier to use an angled setup with more room.)

Cleve54601 (author)2015-01-24

80% full is good for me. I have a huge propane tank out side that feeds my house and they only fill that to about 80% for gas expansion and same with the bbq tanks there only about 80%. On a nice hot day propane will expand my tank will go from 80% to sometimes 93% to 97% (being the highest its ever gotten) on the gauge out side. I am NO expert but the last thing I want is a couple of one pound bottles exploding in my suv as I am driving down the road. So the harbor freight adapter will work good for me and I would recommend it to everyone else. this is a good set up but don't mess with the relief valve you should only have to purge the tank when its a virgin.

Kinnishian (author)Cleve546012015-06-23

The pressure in the tank should be the same as a result of the gas expanding- it is driven by the vapor pressure of the liquid, since propane is liquid in your tank. So a small layer of liquid or a big layer will have the same pressure in the empty part of the tank.

There may be other reasons why they only partially fill tanks though; I don't know.

thedustycelt (author)Kinnishian2015-06-23

Just to clarify, completely full means to bring it to a full pound. There will still be expansion space in the tank.

JeffJ115 (author)thedustycelt2017-05-17

You need to clarify completely full. Because that's what people will assume if they read your directions. I use the exact same setup as in the original instructions exactly. Except for I unscrew the relief valve just so gas can escape and liquid can go in easier. Once liquid is noticed escaping with the gas sometimes just a few drips shooting out then I shut off tank then tighten valve stem usually feel about 90% full. If either valve stem(Schrader valve) leaks on you tap bottle near valve with a wrench it usually re-seats. If I get one on main valve that leaks I put my torch tip on it and use it first. I mark my bottles when I bought them and how many times I fill them. If have one that is a consistent leaker i dispose of it. There are always propane cylinders to be found most people are not do-it-yourselfers and would be terrified of doing such a simple test if you have common sense and are careful.

JeffJ115 (author)JeffJ1152017-05-17

I know Common Sense is not all that common LOL. I live in Utah and when it's cold compared to when it's hot is from approximately 15 degrees Fahrenheit to 120 °F. In my garage. When it heats up and I shake it there is still air space or gas space but it seems like the liquid does not swish around as easily as it did when it was cold whatever that means I don't know but I consciously put less and when it's cold and More in one it's hot because I'm not as afraid of expansion. I don't know the science behind it but that's just me using sense. If they could be filled up completely safely somebody would sell completely full ones period so completely full add one pound if completely empty or just do what I said feel it till it's seems to be around 89%. You'll have no issues. Brass caps with O rings are a good idea for main valve to ensure no leaking especially in transport. I don't understand how unscrewing the pressure relief valve has anything to do with the pressure setting from a factory. Those are sealed when you tighten it. Unless I'm mistaken(rarely). The pressure has to do with the spring on the Schrader valve not the how far you thread it into it's given hole. It's just like the valve on your bicycle tire except for backwards let's let's air or gas in or out into your bike out of your propane cylinder. Pull one out completely you understand.

JeffJ115 (author)JeffJ1152017-05-17

80 to 90% I meant for full. Anyone can tell them all the way like it sounded in the original directions LOL but if you want to risk your family's life and your own and others that's up to you. But safety should always be kept in mind. Putting bottles under water to check for leaks or use something like Snoop to detect leaks is a good idea. You never want gas leaking out in an enclosed area. Will settle to the ground and can easily be ignited if in small area can explode. Long as it burned off slowly would be fine but the sudden ignition is what's dangerous. Refill outside in well ventilated area for your safety had others. Breathing the vapors can kill you and will give you a headache

knowlesjv (author)JeffJ1152017-08-15

Imused the standard adapter that I bought on amazon. Refilled 6 cylinders when the out side temp was in the high 80s. The cylinders filled within about 20 seconds and seemed to have been completely filled, no sloshing of propane. I put one in my car to go camping and while driving smelled propane and then a sudden 1 second burst of propane. I stopped the car and removed and disposed of the cylinder. This leads me to question the safety of this process. Should I release pressure on the other bottles? Should I dispose of the other bottles? Any guidance would be appreciated.


dmmartindale (author)Kinnishian2015-11-29

As long as their is some space for vapour in the tank, you are correct: the pressure is just the vapour pressure of propane at that temperature.

The potential problem is when a tank becomes full of liquid (because it was filled nearly full to start with, then the temperature increased and the liquid expanded). Once the tank is full of liquid, the pressure rises extremely rapidly with further temperature increase, since the liquid is nearly incompressible and the steel tank is nearly unstretchable. If you're lucky, the safety valve will open to release the excess pressure. This releases propane into a space where you're not expecting any, a possible fire hazard. If you're unlucky, the safety valve will stick and the cylinder will explode.

To avoid this, stations that refill barbecue cylinders put the tank on a scale, and stop filling when the *weight* rises to the correct value - one that guarantees enough vapour space remains in the tank even at higher temperatures.

What others are trying to point out is that this equipment and procedure could end up with the small tank almost entirely full of liquid, which is potentially dangerous.

- Dave

use a scale. weigh a factory filled tank, weigh the empty one, and weigh the one you filled. just don't put in more than 16 oz.

RandyJ22 made it! (author)dmmartindale2016-05-24

As long as *there is some space.

Kinnishian (author)dmmartindale2016-04-12

Gah! Just saw your response. Thanks Dave. This makes sense to me. It is however unlikely to be an issue unless you get to 98% or so full, I think. Give or take some tolerance on scales even 90% full should be OK.

My coworker suggested the 80% rule came about because propane went up in costs and people still wanted $20 refills. Blehh, who knows.

Definitively my theory of the domed top wanting axial forces..yeah...That's total BS.

RandyJ22 (author)Cleve546012016-05-24

*they're only about 80% full.

Yolorenzowhatup (author)2017-05-29

Where do I get it

DaveP140 (author)2017-03-10

It's so easy and fast to refill these bottles it's hard to understand the advantage of choosing refilling them to an unsafe 100% instead of a safe 80% for such a tiny amount of propane. If I filled mine to 100%, I'd be concerned that my Weber BBQ might get liquid instead of gas, since the bottle is mounted at a 45 deg angle. Different strokes for different folks.

YumasunbumA (author)2014-09-06

Do not fill a bottle past 80% under any circumstances. You need the expansion room when the gas expands. Been filling them for years and learned from a propane tech the right way to do it.

Kinnishian (author)YumasunbumA2015-06-23

We should look for a propane tech to clarify is. There are a lot of people claiming this but the basis is weak. Propane in a tank is liquid, and that liquid produces a vapor pressure depending on the temperature. That pressure is the same irrespective of the empty space. It's whatever pressure needed for the rest of the propane to stay liquid at a given temperature. If there is absolutely no space in a tank then I could see maybe the pressures would push funny on the tank. But I doubt it.

There could be other reasons to not overfill a tank but I don't think it's quite as clear as everyone is saying it.

Kinnishian (author)Kinnishian2016-04-11

OK: Let me take one more stab at whether the liquid expansion is meaningful. ...

And my second stab failed. What we need is a table of the density of liquid propane vs temperature. Then, you can make the calcs for the "expansion" even conservatively pretending the tank walls don't also expand based on the metal heating up. Unfortunately the best nubmers I could find were only for the density at 25C and the density at -42.12C, from two different sources, suggest 580C and 580.12C. Maybe these are correct, but the difference is really low. A 3.6 gallon tank at -42.12C would become a 3.6007 gallon tank.

I think, we get a lot of anecdotes of people saying the sensor varies wildly by temperature. But, these sensors aren't perfect, and are calibrated around 25C. That could be a very good reason why they show very different numbers based on temperature.

But there's got to be an answer out there, and it frustrates me that I have no idea what exactly is the reason, and most people's suggestions have been anecdotal in explanation.

Please let me know where my reasoning has gone astray, or has just been badly explained.


pchem (author)Kinnishian2016-07-01

I've read a few of your comments and I'd say nice job sticking with the facts on the saturated liquid-vapor lines of reasoning. I don't quite understand the data presented in your post here. You might be underestimating the amount by which liquid propane expands with temperature. We get accustom to water, for example, but without the hydrogen bonding to hold it back, liquid propane expands considerably more easily than our experiences with water.

From one source, the coefficient of thermal expansion for liquid propane is about 0.00155 / C. So, if a tank is filled on the coldest of days (-20C) here in the midwest, then on the hottest of days (40C) the liquid propane will have expanded by about 9%. If the original liquid volume was about 90% of the tank volume, it would now be about 98%. Of course, things could get worse in the trunk of a car on that hot day. To leave a "public safety" size margin for error, it seems the industry aims for 80% fill level. I think this is what dmmartindale was pointing out as well.

High liquid levels may also make it more likely that if some over-pressure condition forces the relief valve open, that liquid propane (now at a boil due to the dropping pressure) might get forced through the relief valve - releasing a truly unexpected volume of propane vapor that might reach a more distant ignition source or displace O2 in some confined space .

I also came across information that the pressure relief valve typically is calibrated to open at an internal pressure of about 375 psi. For saturated liquid-vapor in the tank, this pressure would occur at about 75C (165F). So much for carelessly transporting propane tanks in a closed car.

here is the source for the coefficient (thanks google):

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