Introduction: 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

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

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

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:

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:

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!

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.


thedustycelt made it!(author)2014-05-02

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.)

Yolorenzowhatup+ made it!(author)2017-05-29

Where do I get it

Cleve54601 made it!(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 made it!(author)2015-06-23

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 made it!(author)2015-06-23

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

JeffJ115 made it!(author)2017-05-17

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 made it!(author)2017-05-17

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 made it!(author)2017-05-17

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

dmmartindale made it!(author)2015-11-29

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

stephen.yawii made it!(author)2016-06-20

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)2016-05-24

As long as *there is some space.

Kinnishian made it!(author)2016-04-12

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 made it!(author)2016-05-24

*they're only about 80% full.

SHOE0007 made it!(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.

DaveP140 made it!(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 made it!(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 made it!(author)2015-06-23

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 made it!(author)2016-04-11

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 made it!(author)2016-07-01

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):

AceH7 made it!(author)2017-02-10

you got most of it, But you left out what happens in that head space... at ~94% @ 10 c the vapor pressure of propane is about 120psia, and then at ~98%, that gas has been smashed into one third the space, raising it to 360psia, easily blowing the safety valve. At 96 c propane will not condense into a liquid, near 96 c propane will not easily nor quickly condense into a liquid. If you raised the temperature very slowly it is possible that you could get enough condensation to keep from blowing the valve, but that condensation still takes up space, so you are actually at 99+% full. Furthermore, thermal expansion is not linear near the boiling line.

Kinnishian made it!(author)2016-07-25

Wow, Pchem, I appreciate the response! I had not considered the concept of H-bonding making water a particularly volumetrically stable state. Instead, I was mostly basing on my experience reading about metal molding and that the pouring at X degrees C vs (X+100) degrees C usually won't make a meaningful difference in volume contraction (it's all in the phase change.) That said, the liquid of metals would have a lot more effective bonding. (by the way, just to clarify, when pouring metals usually the mold is 1-3% larger than your desired object due to the metal contracting as it solidifies. Also because there's often a lot of surface finishing to do.)

When I wrote my initial comments I had been attempting to find data for the expansion of propane with temperature. The only data I remember finding was between a small celsius range, (like 20C and 30C maybe?) and so the error in the posted numbers could have been all I was seeing. I wish I had found the coefficient of expansion that you found. Because whatever I found suggested much less of an expansion.

I also went down a couple other lines that were just nonsense and I sort of wish I could edit or delete without obscuring the line of comments. That may be partly where you're confused by my data presented.

I think your analysis is very cool and I appreciate it. I do wonder if the significance of 9% would go down if you in turn also counted the expansion of the tank dimensions itself, but maybe that would be very insignificant as previously mentioned, the metal inter-phase does not have meaningful expansion at this scale.

SteveW153 made it!(author)2016-04-11

I'm a gas fitter and propane tech, don't fill past 80%. They came up with that number when engineers filled a tank to 90% and then raised the temperature half a degree. The psi went from 125 to over 400. The empty space is needed to buffer the expansion. Or else you get the 'can of beans in the fire' except with propane instead of tasty beans.

Kinnishian made it!(author)2016-04-11

So you may be a propane tech, but I'm still fairly confident this is a case of repeating conventional wisdom without being correct. The pressure is *the same* for a *given temperature*, expansion space or not (pretty much up until you are 99% full* [there is a case this is not true give me a sec I'll mention it later].) Let me back myself up with a table:

I think, if anything, the reason is that the hemi-sphere dome of the tank experiences a pressure that is expected and desirable to be pulling on the cylinder in a lateral way. When you fill above the cylinder where it starts doming, that means your unbalanced force is pushing on a curved service. But I also question whether this can be the case, because if it was a real concern, tilting the propane tank would be dangerous. It's obviously not.

*Here's the case where I mentioned that the pressure is not necessarily the same for a given temperature, irrespective of the volume available for gas: Technically the metal of the propane might have a different thermal expansion coefficient, *and* the *liquid* propane could have a much bigger thermal expansion coefficient, and the propane would take up more than the volume of the tank. But because interphase expansion cofficients are much smaller than interphase expansions, this is unlikely an issue unless you're at weird tank geometries or extremely full like 99%.

I hope my post isn't too long and better explains why I still don't buy the explanation given.

creidenouer made it!(author)2017-02-08

Thanks very helpful. Question, should I be using thread tape in general, even on green bottles attached to appliances? If so, what about tru-blu?

tjfoley made it!(author)2017-02-05

I own 1 500 Gal., 2-100 pound, 2-40 pound and 1-20 pound Propane tanks they all have something in common with the 1 pound tanks The burst strength is 450 PSI or better and a safety valve that is set for 250 PSI Using the 20 pound tank at apx 60 deg. F and the 1 pond at 0 Deg. F the most I have gotten is at filling with out touching the safety vale in a time of 1.5 Min. apx 11.5 OZ of Propane in the cyl. (Spring type scale not sure how precise it is) So you can see how hard it is to blow your self up by over filling the tank. If you go by weight and do not exceed 1 pound you will be ok. Your 1 pound tank has the capacity of 19.2 OZ the 3.2 OZ is your vapor area and safety expansion zone.

frisbrob made it!(author)2016-11-14

Hey, I don't think people understand how any size propane tank is refilled. If you have ever taken your propane tank to a refill station, you will notice that they hook the hose from the big tank and pump to your tank, they open the valve on your tank and start the pump, at this point you will notice they take a screw driver and open a vent on the side of your tanks valve, at this point gas is escaping and the liquid propane is being pumped into the tank, they know the tank is full when the liquid propane starts to blast out the small vent and they close it with the screw driver, then they close your tanks valve and turn the pump off. Now the tank is not all the way full like you would think, there is still head space in the tank. You fill the small 1 lbs tanks the same way, when the liquid propane starts to blow out the vent it is full, there will still be just the right amount of head space in the bottle, that is the way they are filled at the factory. If the vent is open , it will not over fill and if the vent is closed the bottle will pressure up and not let anymore propane enter the bottle. So you don't need to get on your computers, get calculators out, do a months worth of rocket science math to figure out how much propane can go into the bottle.

Arhude made it!(author)2016-11-13

I used needle nose pliers as you suggested and the valve would not re-seat, no matter what. All gas leaked out. I think unscrewing it would be better.

gri2a made it!(author)2016-06-20

I use a very similar method to refill 1 lb bottles... right angle valve for decanting and forceps to open relief valve. Using this method its quite easy to overfill bottles and I see a lot of talk about how much to fill/overfill a bottle.

I have a very simple rule of thumb. I weighed a bottle when I bought it. It was 880 grams (31oz). (I'm from Australia and we've used metric for the last 30 years).

When I refill a bottle, I weigh it. If its close to (but not over) 880grams, then its fine. I put back on the cap and its ready to use. If it weighs more than 880g I bleed off* some of the liquid until its close to but under 880g. Job done.

In short, I bring them to the weight of a new bottle, a little less but certainly not more.

* If the valve is up, you are only going to bleed off gas. With the bottle up-ended and the valve pointing down, you will bleed of liquid, which has all the weight

stephen.yawii made it!(author)2016-06-20

i just ordered everything i need from amazon. my local stores don't have all the parts I need.

dougpeot made it!(author)2016-04-07

In regard to the pressure relief valve and using an angled needle nose pliers to vent the 1lbers .... the LP can create an "icing" on the valve seating ring - if the valve doesn't re-seat try a little room temp water ....

KerryF14 made it!(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.

GeeDeeKay made it!(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 made it!(author)2013-10-30

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 made it!(author)2013-10-30

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 made it!(author)2013-10-30

"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 made it!(author)2013-10-30

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 made it!(author)2015-11-21

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.

jtrzaska made it!(author)2014-06-25


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 made it!(author)2013-10-30

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!

RobertJ26 made it!(author)2015-08-27

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 made it!(author)2015-08-27

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.

KylaR1 made it!(author)2015-08-20


From AmeriGas Propane:

"A propane container absorbs heat directly from the surrounding air.

It’s not uncommon for a container’s pressure to change. Propane liquid can increase more than 50 pounds of pressure or more in the course of a day, without an appliance operating. Propane liquid, like water, will expand when heat is added to it.

Containers are generally filled to about 80% of their capacity to account for effects of pressure and temperature.

This leaves space above the liquid for the propane to expand freely as temperatures change without danger of the container becoming over pressurized.

A propane container that is filled beyond the fixed maximum liquid level gauge may be at risk for an unintended propane release."

Propane expands at nearly 17 times greater than water, displaces oxygen and is an asphyxiation hazard if inhaled. Propane is odorless and colorless. If you have a 1lb. cylinder releasing excess pressure in your vehicle on your way to a camp site, you won't know it, and you and your loved ones will likely not make it to your destination.

Jose+RomanT made it!(author)2015-08-02

This is a dangerous procedure: This is an instructable on how to overfill a tank! Completely filled cylinders are dangerous as they don't have room for expansion once the temperature increases.

Propane/butane approximately liquifies at 32 psi at 20 °C (68 °F), and 320 psi at 55 °C (131 °F). That's a 10x increase in pressure for a 23 °C change in temperature. Please be careful.

Just top it up by weight. Check the weight on the label and never exceed that rating. And if you happen to overfill it, just reverse the process (big tank right side up).

ken.mchale1 made it!(author)2015-03-09

The plumbing above works. Only thing I did different was use a 1"-20 cylinder thread and soft nose excess flow POL with handwheel instead of the male POL fitting to 1/4 MIP above (top right in illustration) (Mr Heater sells them and Made in USA). The 1/4 street elbow was also changed to one end male one end female to accommodate !"20 excess flow POL. With the POL you can slide it into position and tighten without rotating entire fitting for easy alignment. I also don't mess with the relief valve, instead buy a pair of "curved" locking forceps (like medical) and pull up on the pressure valve (as described with vent tool above) while filling until you see a small burst of liquid vapor. The 1 lb bottles finish out within 2 oz. Be sure to use YELLOW thread tape designed for gas fittings. :)

thedustycelt made it!(author)2015-03-09

Excellent modifications :-) You should post a pic of your setup :-)

I also went and changed up the text in my original instructable regarding venting the tank. some people don't read the stickies in the comments.

mmartin40 made it!(author)2014-06-13

Although too scared to do myself, but VERY nice! Do you know a good valve to stop the camp tanks once they are only used partially from expelling the rest of their gas ?

Cleve54601 made it!(author)2015-01-24

when you unscrew the 1 pound cylinder the valve should close automatically if it leaks gas you should throw the tank out.

sbaker28 made it!(author)2014-11-26

For those of you so called "experts" it is clear that being "certified" has also Brainwashed you into believing that what you are taught is the only way. It is clear that you have been taught how to also not think for yourselves.

If you read the label on the bottle you will see the weight of the gas inside the cylinder. here in Australia it is 426g so there is just under 1L of propane in the cylinder. I have been filling these cylinders for around 2 years now.

What I will do is exactly what thedustycelt has shown. Before and after I have finished filling the cylinder I weigh it every time and I get a weight change of 400-420g in the cylinder. This is the 80% mark that you all bang on about with your wasted time becoming "certified".

If I was to buy new cylinder every time @ $10 a go, the cost of using these would be beyond reasonable. I see it as a way camping and chain stores gouge you for the convenience of having a portable gas cylinder. I also refill my regular cylinders myself using an adapter mounted in my car and go to the local service station, a camping store will charge $28 to refill a 9kg bottle a 9 kg bottle will hold 18L of gas here in Australia gas is currently $0.74/L there is an immediate cost saving. there is an even bigger saving with the 45KG bottles a local gas supplier charges $130 for a full cylinder. I can refill the same cylinder for around $67 as fuel prices fluctuate this changes.

I don't know about you but and extra $60-$70 in my back pocket is worth the trouble of a small bit of math and a little plumbing. Two refills of the 45kg bottle and I have paid for the filling hardware, so it pays for its self very quickly.

The gas at the service station is more refined than the BBQ gas your local camping and hardware stores sell, so its better for your equipment

TSellers22 made it!(author)2014-11-25

When using dichotomous cooling of the slave and donor tanks, it is possible to overfill the 1lb tank using the conventional adapter, that's why a scale should be used. The connection fittings are best if bridged with a flexible hose which then allows you to float the receiving 1lb tank on the scale. Once you place the bottle on the scale and zero it out, you can then monitor the net weight as the bottle fills and halt the process at 16.4 oz. Then confirm the gross weight which should be the sum of the tare (the weight of the empty bottle), and the net. If it is over, you then use the pressure relief valve to adjust to your target volume.

Nunofyourb made it!(author)2014-11-10

I just use the HF refill kit but leave the 1lb bottle on the 20lb donor tank for about an hour and I beleive this fills it to about 90% +.I have had no bulge problems and refill most bottles about 6 times before they decide they no longer want to be refilled.Also helps to warm the larger donor (grill tank) and keep the smaller 1lb tanks cold before you refill.Good luck and keep refilling......


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