The Truth About Filling 20 LB BBQ Grill Propane Tanks

Posted September 02, 2012 by Jim Ciallella


Few people know I was a mean propane filling machine in my high school days at Taylor Hardware. As a result, I know a few things about tank tare weights (an empty tank's weight) and other propane lingo.

For the last 7 years I had my trusty Weber grill hooked into a 500 gallon underground tank at the house in Taylors. When I moved earlier this year to an all-electric house I had to switch back to a standard 20 lb BBQ grill tank. I also considered 30, 33, 40, 60, and 100 pound cylinders, to avoid refilling as often. I found that new 30 or 33 lb cylinders are at least double the price of a 20 lb, and finding lightly used ones on Craigslist wasn't happening.

I picked up a new 20 lb tank at the Home Depot for 29.97, minus 10% off competitors coupon and a 10% discount on a gift card purchased on eBay. (Costco sells tanks for 28.99 compared to Amazon's roughly $45). Now, where to fill it?

A Little About Propane Tanks

These "20 lb" tanks are designed to take up to 20 pounds of propane. You may get a pound or 2 less, depending on the temperature of the tank and surrounding air when the tank was filled. Cooler = more propane in, hotter = less in. Tanks can actually fit another 20% in the tank, but that extra space is designed for expansion as the temperature rises.

In very cold winter climates, like Canada, there may be more concern/rules about filling a tank to a complete 20 lbs. This is because if you leave a tank outside in very cold temps, filled the tank when the tank is cold, and then bring it into a hot basement/garage for a space heater, the gas will expand as the tank warms. With enough of a temperature increase, the tank's pressure relief value will release a bit of gas. This would be less of an issue if the relief value were bleeding to outside air.

Propane Tank Tare Weight on Collar

All propane tanks have a "tare weight" or "T.W." stamped on the collar of the tank. For a grill sized tank you simply calculate the tare weight + 20 lbs, and that's how much the tank should weigh when it's full. Most 20 lb tanks have a tare weight of +/- 17 pounds when completely empty. This means a "full" propane tank should weigh about 37 pounds.

There is also a month and year on the collar indicating the date the tank was made. For 20 lb propane tanks, you have 12 years from the manufacture date before the tank must be re-certified with a new date stamped on it. The re-certification only adds 5 years before having to re-certify again. The cost and inconvenience of re-certifying almost always outweighs the price of a new tank.

Brand new propane tanks may come with air inside and need to be "purged" before the first fill. Some newer tanks, like Bernzomatic, will have a sticker on them saying they don't need to be purged within 6 months of the manufacture date.

Purging requires a special adapter to allow a small amount of propane in. The pressure then pushes air out of a one-way bleeder valve. Purging may add another $3-4 dollars to a new tank, though some places don't charge, especially if you buy the tank from them.

The Math on Refills at Costco

Internet searches suggest the following:

  • 1 gallon of propane weighs 4.2 pounds
  • A "full" 20 lb cylinder should have 4.7 gallons or propane in it

I called around and the local U-Haul place wanted $16 for a refill. I remember Costco has a sign for $9.99 refills. I thought I was getting a great deal, but it turns out I pretty much got no deal.

Costco 20 lb Propane Tank Receipts

Costco in Greenville, SC is a bit deceiving because they first hand you a slip that says "20 lb cylinder". When you pay inside the receipt says "20lb PROPANE", and the filling print out says "Cylinder: 20S lbs." The only defense is that the filling print out is honest and says "3.6 gallons". However, nobody knows off the top of their head that a propane tank is supposed to have 4.7 gallons to be considered "full". By saying 3.6 gallons, they are masking the fact that they put in 75%. If they wanted to be upfront they'd say "we will put 15 lbs of propane into this 20 lb cylinder".

This means Costco puts in 15 lb of propane.

Costco fills propane tanks to 75% of capacity
3.6 gallons / 4.7 gallons = 75% of the normal fill.

or, said another way

(4.2 pounds/gallons) * (3.6 gallons) = 15 pounds

The word on the web forums is that the Blue Rhino and AmeriGas similar exchange services put in 75%, or 15 lbs.

If you do the math on Costco, it's actually not a bad price. It's in line, if not cheaper, than paying $16 for a full 20 lbs. Though, Costco's use of the "20 lb" phrase is unfortunate. I think their motivation is to have a cheaper price, so members think they are getting a great deal. Plus, by only filling 75% they make members come back more often, and go inside to shop while they wait.


  • If you're looking for the best price, owning a propane tank and re-filling it is going to be cheaper than using an exchange service. As always, you pay a premium for convenience.
  • Ask how much propane is going into the cylinder. There should be 20 pounds going in for full capacity.
  • Weigh the tank when you get home and it should be about 37 pounds. If it weighs 31-32 pounds then you know they only put in 15 lbs of propane.
  • Costco's propane price is still fair when you do the math.

Bonus - Weber Grills

I also assembled the grills at Taylor Hardware. Weber Grills were by far the best we sold. Reasonable care and a cover will easily give your Weber grill 10-20 years of life. You can buy other cheap brands and they will have steel parts that rust out in 2-3 years. You can buy a fancy looking stainless steel brand from Home Depot and it will likely not rust, but it will cook unevenly or the handle or wheels will break off and you'll be back to the store in 5 years for a new grill.

Bonus - Side Burners

I also helped sell the BBQ grills. We sold a few with side burners, but we never pushed them. I recall many conversations with customers who had paid more for a side burner in the past and never used it, despite their best intentions. Chances are that you will use the side burner once or twice, so don't spend the money unless you are absolutely sure you're going to use it


Evan Tishuk ~ September 03, 2012

This post perfectly illustrates why we love Jimmy and what he brings to the table.

Tatt2Jack ~ July 09, 2014

The Silver series Weber we have has been turning out great food (not dry or burnt. NO, not all grills Cook the same!) for 15 years and we've only replaced the "Flavor Bars" twice and that little push-button igniter finnaly died. AND its kept outside year around. Best $$$ we've ever spent. Most people think a Grill is a Grill, but a Weber puts out food like no other grill. you get what u pay for.

Dan ~ October 10, 2014

I learned this today and found your page trying to see just how big a difference it is going to be. wish I had found it long ago.

Chip Nimmons ~ September 10, 2012

I filled thousands of these in a prior life. You are only supposed to fill them to 80% water capacity(5 gallons in this case). I always filled them to 38 lbs, but that was the weight with the filling mechanism attached. If you tried to over fill them the built in Ralph Nader device would shut it off. Even then, sometimes in hot weather the gas would expand and trip the pop off valve and bleed off some gas. Full capacity should be about 16 lbs of gas, we had a scale for tempature that varied the amount. We never used it. About 10 years ago they added additional Nader that prevents from filling too full with a float controled valve inside the tank, so it's nearly impossible to get more in there anyway. You could ask the guy to open the bleed while he fills it and it would help.

Chip Nimmons ~ September 10, 2012

Side burners are great for frying things!

C-Town ~ September 12, 2012

Great post. I remember a couple years ago my dad bitching how they don't fill up propane tanks anymore. I guess he was right, not that I was doubting him. Thanks Jimmy.

ShelbyBob ~ February 02, 2013

Our local U Haul locations sell propane for 3.99 a gallon with means a 20 lb fill up will cost you the same as Costo but you have 20 lbs in the tank which means a couple of less refills during the season.

MikeP ~ March 03, 2013

I just found last weekend that Tractor Supply sells by the gallon also, most places have a flat fee currently $17.99 at Agway, $18.99 at my local True Value and up to $20.99 at a Rhino exchange matter how much they put in whether is 3 gals or 4. I just had a 20lb completly empty tank filled yesterday at TS, I watched the meter as it was filling and it stopped at 4.6 (4.7 is supposedly max full) and their price per gal. right now is $2.49 so the bill was only $10.45 for a FULL tank. That's pretty hard to beat and you can see how much they actually put in. So if you have a TS near you, I would suggest giving them a try for your next refill

Dan ~ March 07, 2013

Since COSTCO now sells tanks with a gauge included, what does the gauge register when they "fill" it?

If it is accurate and what you say takes place, the gauge will show it is not full.

Seems odd they would sell a tank with a gauge included if they are not filling it?! In other words, they are providing us with exactly what we need to "catch" them. So can we trust the gauge? I'm confused.

I also wonder if this varies by state; I'm in CA, and need to buy a tank.

Jim Ciallella ~ March 07, 2013

Dan, I haven't see tanks with a gauge in them, so can't reply to that.

I will say that around 2000 the hardware store I worked at sold gauges you screwed into the top of the tank. I recall seeing a number of them in the returns bin.

The older model Weber grills used a spring loaded hook, on which the tank would hang, and it indicated the fill level. It's wasn't precise, but good enough to tell 3/4, 1/2, 1/4.

Weight is the only method I'd trust.

Jay ~ June 27, 2014

The gauges are a rough approximation vast majority of them DO NOT WORK they are marketing gimmicks nothing more, Only by weighing it can you tell the exact content amount even larger cylinders with gauges like a 33# (tow motor) are aren't accurate

Visitor ~ November 26, 2014

Guages measure head pressure and are there for useless on a propane tank, which contains liquid and builds more pressure with temperature increase.

Visitor ~ March 15, 2013

But really. Who cares. It's $5.
Just buy a starbucks coffee and you've made the difference

Another Visitor ~ March 22, 2013

I'd rather burn a $5 bill than have someone steal it by being dishonest. And, I don't buy starbucks. Thanks OP, you offer good info. Others can waste $5 at starbucks if they wish,
I want my tank full if I pay for it to be full, whether it is propane, diesel, or gasoline. YMMV
Interesting info, thanks...

Visitor ~ November 11, 2014


Visitor ~ April 09, 2013

yep, it's $5. and after this happening to you 20 times in a month, that's $100.

Not to say you're consuming 20 tanks of propane, but this philosophy of "who cares, it's only five bucks" results in people wasting tons of money on stuff, and it emboldens vendors to jack prices up a bit more than what the market should bear.

My wife has this philosophy quite often and it just chaps my a**. I was raised to support the shop that charges you less, so that he stays in business, and maybe the guy who charges more will have to bring his prices down to remain competitive.

John Brattain ~ March 25, 2013

My wife found a gas company that refills 20 lb tanks for $14.00. I went with her today to get two tanks filled. I watched the gallon meter instead of the scales when the tanks were filled. I doubted that we got full tanks. So, out of curiosity, I Googled the question and read the article above. My tanks have an eighteen-pound tare weight. After filling, they weighed almost exatly thirty-eight pounds. Doing the math, we got twenty pounds of gas in each tank, and the price is $0.68 per pound. The Costco price is $0.66 per pound. Not a bad deal at the supplier she found, and much less trouble than going to the nearest Costco.

Andrew T ~ April 04, 2013

Anyone who actually fills with 20lb of propane is an idiot and also is doing so illegally by law 80% is maximum full. Most 20lb tanks have a 47.6lb water capacity propane weighs .42x water weight so 47.6x0.42=19.995lb capacity of propane and at 80% fill 19.995x0.80=15.994lb of propane at a legal fill. 15.994lb+average of 17lb empt tank weight=~33lb so anyone with a tank that weighs upwards of 36-38lb should be worried about having the pressure safety valve pop and blow off gas. By the way I'm not just talking out my ass I've been in the propane industry for almost 12 years now, and have trained hundreds of people.

Visitor ~ April 09, 2013

Then why would they call it a 20# cylinder? Reason indicates it is because the cylinder is sized to accommodate 20# of propane. Calling people idiots when there's good reason for their argument is, well, idiotic.

If you mean to say that you used to be able to put 20# of propane in a 20# cylinder years ago, but since then new laws or increased knowledge no longer permits this, that would be a much more fair statement.

Jim Ciallella ~ April 09, 2013

What is a propane expert doing trolling on random blog posts?

One would imagine:
A) Said person is very concerned about people's safety and calling them idiots, despite evidence to the contrary, is the best way to spread safety
B) Said person has a vested interest in people believing otherwise
C) There is a disagreement on legal vs practical
D) Tank designs have changed significant since 2000, most likely the result of lawmakers attempting to protect the world's real idiots, the folks who find a 1 in 50 million way to explode a 20 LB tank.

I'm willing to learn, so if there's facts to be share, please share them in a manner that makes the statements believable. Preferable without referring to people as idiots.

Here is my rebuttal. Everyone agrees there's empty space in the tank to allow for expansion, and 80% is the number often used. No argument there.

Since at least the late 1990's there have been floats in the tanks. I recall filling tanks and if I was jibber-jabbing with a customer it would click and stop filling. If it clicked we'd have to turn it upside down a couple times to force it to reset it. However, this float would not click off near 15lbs, more like 20lbs.

Since the 90's the tanks also have a mechanism in the threaded part which is depressed when a regulator is screwed into it. You can push that piece in manually, but it mainly prevents situations like a kid opening a spare, unconnected tank and having it bleed gas into the surroundings.

I also understood there to be a slow leak detection component, for instances like when squirrels chew through the rubber regulator lines and cause a small leak. I don't know this to be fact.

There's also a spring loaded pressure release value on the back of the tanks. If you leave a "full" tank on in the sun on a 100 degree day it's not un-common to smell a little gas coming from the pressure release. I don't deny overfilling has dangers, it's pretty hard to overfill a new style tank between the float and the pressure relief.

That leaves us to determine if disagreement is about what is "illegally" done, versus what can/is done in practice. I could honestly give two rips about the legal side. I trust engineers 3000% more than politicians and lawyers.

If the the engineers who designed the tank added a float and calibrated the pressure relief valve, and those are working, then retailers should put in as much as possible without tripping the float.

That retailers fill tanks well below the limits of the tank's design, and call it legal, would seem to be the most likely case.

Please share your thoughts on the disagreement and include facts more than legal talk.

Visitor ~ December 05, 2014

So much good math, one failed constant and so many mis-trained propane consumers. Water is 7.5 llbs per gallon not 10 lbs per gallon. Propane is 4.2 lbs per gallon. That makes propane .56 times as dens as water, not .43 times as dense. Your multiplying factor should .56 instead of the incorrect .42.

Jim ~ December 07, 2014

I'll defer to my original simpler equation in the original post.

Robert ~ December 13, 2014

I am an engineer. We use water weight as 8.34 pounds per gallon to design things.

dhgasman ~ April 15, 2013

I have worked in the propane industry for 28 years now. Currently I am an Operations Manager. I have trained many employees over the years on filling propane tanks from 5 lbs. to 30,000 gallons. The tank most certainly is a 20lb cylinder thus stated because of the amount of gas the cylinder can hold. If Andrew would fill by the three safety methods we use he would understand the cylinders very slightly but hold approximately 20 lbs of propane safely. You set the scale 20lbs above the tare weight plus the weight of the style of filling valve you use. While filling you should open the 80% outage gauge. This provides three safety measures for filling. 1- you have the Overfill Protection Device as part of the cylinder valve internally to stop the filling process. (Which I have seen fail more than one) 2- You have the scale to trip at the preset set amount. 3- you have the 80% outage valve which will spit liquid if overfilled. Now Andrew should know what a 80% outage gauge is since he is so well versed in properly filling propane tanks. So the next tank he fills one he should fill using the outage gauge and then weight the tank. He may be supprised how long he has been being taught to rip off his customers. This outage gauge is a tube that travels down into the tank 20% from the top. All larger residential tanks are also equiped with this.

EngineerGuy ~ May 11, 2013

Jim's conclusions are accurate. A 20 pound capacity tank having a Water Capacity
of 47.6 pounds can safely hold 20 pounds of liquid propane with lots of empty space
above the liquid. Let me provide conclusive proof :

Tank will hold exactly 47.6 pounds of water and water density is 8.33 pounds per US
gallon. Therefore the TANK VOLUME IS 5.71 US gallons total.

Liquid Propane at reasonable temperatures has a density of 4.24 pounds per US
gallon. Therefore 20 pounds occupies 4.717 gallons of the tank volume.

The % of Tank Volume occupied IS : 4.717 divided by 5.71 => 82.6 % .

Where Andrew T went wrong (his reasoning is fine) is in using 0.42 to represent
the relative density of Propane. The correct quantity is 0.51 . That is to say that
liquid propane has 51% the density of water. If we use that approach :

Tank filled ALL THE WAY UP with liquid propane holds 47.6 x 0.51 = 24.276 pounds.
Then 80 % of that is 19.42 pounds....again we are close to the 20 pounds.

The industry uses 0.42 to provide a one step method to calculate the safe fill
weight from the Water Capacity. Here we have 0.42 x 47.6 => 19.992 pounds.

I hope this clears up any doubts about the fact that 20 pound tanks are properly
designed to hold 20 pounds of liquid propane ! I see that many others more expert
than myself know this.

I just exchanged a tank at Walmart in Canada and as per Jim's analysis they sold me
a tank with 17 pounds in it. That's not too bad, I'm only short 3 pounds !

(I am sparing all who read this the pain of dealing with metric and Imperial measure.
My Walmart exchange was actually 7.7 Kg. )

Visitor ~ May 12, 2013

I recently got my propane tank refilled for my grill. Now when I am grilling the line attached to the propane tanks frosts up. I called a local propane place and they told me the person overfilled the tank but it is still safe to use. Last night I was grilling and propane was squirting out of the hole in the round metal device that connects to the propane tank. I am starting to get nervous using this tank. What should I do?

Visitor ~ May 15, 2013

Dear Jim: Is there a device or meter that we can put on our 500 gal propane tank so that we can see how much propane we use. Our tank is above ground and services our entire home. We are gone several months of the year and no propane is used. (tank is turned off). When we got home we received an enormous bill from the propane company and we just don't see how this could be. Also, it would be great if this device or meter would show us how much "actual" propane is put into the tank when the company comes to fill it.

Hope you can answer this question. Thanks in advance.


Jim Ciallella ~ May 15, 2013

Visitor (with the frozen tank),


If something is freezing then there may be a leak, which is a dangerous situation. Do not continue grilling with a leak. I'd recommend checking the freezing area and make sure it's not simply a hole in the rubber hose (squirrels like to chew through the hoses) or a bad seal between the regulator and the tank.

There are possible situations where the regulator would frost up. See this post for more info.

If the tank is truly overfilled then it's possible the overfill value isn't working, in which case it's probably worth returning the tank to a filler and purchasing a new one.

The 500 gallon underground tank in my yard came with a dial gauge that shows the % full. As with a 20# tank, the propane delivery company fills this tank to 80% (max of 400 gallons in a 500 gallon tank).

You'd surely need to ask your propane company to install such a gauge. I doubt there's a DIY solution, and even if there was the propane contract likely prohibits modifications to the tank.

Visitor ~ May 22, 2013

I have also had liquid propane squirting out the regulator and the tank frost up.
I believe it was due to the tank being overfilled - but don't know for sure.
I just had one filled today and saw that the meter said 4.6 gal.
So now after reading the posts here, I'm thinking that I'll have a problem with this one too.

Don ~ May 27, 2013

Hello, I just would like to know how to identify if my tank is still good to be used, I was told that the numbers on the "collar" are the expiration date, but I don't know how to read them, I have two tanks and one has "10CW907E" and "TW18.3" how do I know if this tank is still good to use. The other one has the number like this "4BA 240 02 92" "TW18.4" and "WC47.5" can anyone help me to identify the date?
Thank you.

Jim Ciallella ~ May 28, 2013

TW is the tare weight, as shown in the original post, so that's not it.

The other numbers mentioned do not look like an expiration date. The stamp is usually of the form, MM-YY.

Example, 02-07 would mean February 2007. Look on both sides of the outside of the collar.

Do a Google image search for "propane date stamp" to see examples.

Here's more info from Don Wheatley

Nice post on "Filling a 20# LPG tank". Just wanted to add this. Our local camping supply store fills tanks. You would think they would be the most expensive but at the time of this info they were not. They were filling to the "auto fill shut-off" and their scale read 34 or 35 lbs. I asked about the T.W. (used to fill them too) and the attendant told me that, in New York, the legal transport limit was 17 lbs. without permits and or placard signs, if you could even get them for a passenger car. So by only filling to 34#s they were staying, for my benefit, within that 17# limit. I took him at his word even though, back in the 1980s, I used to bring a 100# tank in the back seat of my car to my uncles to get it filled. Upon reflection however, that 17 lbs. began to not ring quite true when you think about travel trailers and RVs carrying 2 30# (or bigger) tanks, regardless of where they are mounted. Now it may very well be that you are not allowed to transport more than 17#s of LPG in a "passenger car" or SUV or even a "pickup truck" NOT designed to have a propane cylinder on board AND because travel trailers and RVs are a different class of vehicle, by default, allowing for the 2 tanks without incurring a traffic violation. In conclusion, Losing (it really was not "full") or gaining (it was more) those 2 lbs. of LPG did not make going the extra distance to get it from them any real bargain. Now, as of 2013, I get a "FULL" 20# refill for 17 bucks and change at my LPG supplier. AND, that includes sales tax. They actually have one of those exchange racks and because they are in the "biz" they don't care if I bring an old style (no over fill protection) or an expired date cylinder. Their guy just takes care of it and the tanks don't end up in the landfill. FYI - you can take ANY old 20#er to one of those exchanger rack places and, as long as you pay cash, there would be no way to figure out who stuck them with a tank needing a refit (new overfill valve) or rectification. T T F N I like cooking too, DW P.S. - I use the side burner just boil water, in the summer, so I don't overheat my kitchen. Don't forget, you need to figure stuff like that into your AC calculations.

Visitor Andy ~ November 30, 2014

I have an old fish fryer. The fryer hose fitting does not fit the new style 20lb propane tanks and I was told my old tank cannot be refilled. Is there an adapter or a new fitting I can install on the hose to connect with new tanks?

Jim Ciallella ~ June 16, 2014

I bought a spare tank to avoid running out and to avoid the situation where you bring back the tank with gas still in it and pay full price for a partial fill.

Some locations will charge per gallon, instead of per fill, so the later concern may not be an issue.

In any case, here are a few prices from the Greenville/Greer area as of June 2014.

Dobson Hardware in Greer, SC $19 + tax = $20.14

U-Haul in Greenville, SC on Wade Hampton Blvd
$3.79 per gallon * 4.2 gallons = $15.92
$4.99 for a purge of a new tank (* some new tanks are pre-purged)

Mobile Bottle Gas in Greer, SC near Hwy 80
$15 per fill (it sounded like they do partial fills too)

* The newest tank I purchased has a sticker and a note on the plastic wrap saying the tank was pre-purged and that purging was not necessary within 6 months of the manufactured datestamp on the collar of the tank. Mine is stamped 03-14, so I don't have to pay to purge.

Visitor ~ June 22, 2014

I work for a Propane company and we refill the grill bottles...The new OPD (Overfill Protection Devise) valve is a government requirement. This valve shuts off when you reach 80% of full...Personally I think it is a good thing, it keeps the tank from leaking when the temp gets too high and the internal pressure get so high the "pop-off" valve pops off....
The gauges on these tanks are just like the one in your car--It keeps you from running out. They are not very accurate as to the exact gallons left in the tank. Funny thing about Propane, it is sold by the gallon but the gauges show the percentage left in the tank. For example if you have a 250 gal tank and the gauge reads 20, you have approximately 40 gal of propane in the tank....The gauges that screw into the tank reads pressure..On a cold day the gauge might read half full, on a hot day it might read 3/4 full. The new tanks with the gauge are your most reliable...the gauge is hooked to the float inside the tank, but once again the readings are approximate
JUST A SUGGESTION----When you take you tank to be refilled make sure they fill until the OPD valve stops the flow of gas into your tank. This will insure you are getting the full 80%

Visitor ~ June 26, 2014

Great post.. The sad reality about being short measured here, in Canada,
If you complain to Measurement Canada(formerly Weights & Measures) they will do nothing about it.

Visitor ~ June 30, 2014

Very informative article and comments.

Do 10 lb tanks need to be recertified as well after 12 yrs?

Jim Ciallella ~ July 04, 2014

It seems like only the larger tanks, like 100 lbs didn't need re-certification, or at least not every 12 years, so I believe the answer is yes, the smaller tanks follow the same rules.

Visitor ~ July 04, 2014

I stumbled on this by accident seeing if there were any complaints about my local filler. The 20 lb question is answered several ways here. I drive a tanker for a living, and also pressure bottles hauling...propane! If I have an 8500 gallon tanker, and it is 66 degrees outside, I can fill it much higher than if it is 100 degrees out. The 20 lbs is under ideal conditions. It is directly related to outside temp. This is why it used to be you would want to fill your car tank in the morning. Fuel stored in above ground tanks would heat through the day, and you would get less than a gallon over 66 degrees. It worked the other way to. Under 66 degrees you would get more than a gallon. While in your car this isn't a huge deal, with bulk it is enormous. There are days I can move 100000 gallons of fuel by tank. The racks we load at in bulk always have adjusted for temperature. If we order one gallon we get one gallon. It will just take up more or less room in your tank depending on the fuels temperature. That is where the 80 percent fill comes in. Suppose you filled at 50 degrees and it sat there and heated to 90 degrees. If it was full to start, you would have a deadly situation on your hands. As a side note, if you are in Canada, their tanks all adjust to temperature by law.

Jim Ciallella ~ July 04, 2014

Right, so on a 20 lb propane cylinder, it is full when there is 20 lbs of LP inside. That leaves a 20% buffer space in the tank for expansion. The overfill float will click the tank off if you try to overfill it, which stops around 20 lbs of LP. Is that also your understanding?

Visitor ~ July 08, 2014

no the correct full amount for a 20lb propane tank is 18 pounds..

Visitor ~ August 20, 2014

EXACTLY! Finally the right answer. TW- 16.6 + 18 LP = 34.6

I have been filling BBQ tanks for 10 years. I always use the bleeder. If you are waiting for the OPD to go off, you have over filled. When the bleeder has a nice stream of propane coming out the tank is full. That is the safest way to go.

We fill our tanks to the MAX 18lbs. Amerigas and Blue Rhino 15 lbs. Other competition 17lbs. At a gas station you get the best deal. I deliver and swap tanks regardless if the tank is a 1/4 full. At a gas station their starting point is from what ever was left in the tank before you got there.

I hope this helps

Visitor ~ July 08, 2014

Well here is something that I find disturbing that these exchange companies are using outdated tanks I recently purchased a refill tank that was dated 7/00. Though the tank are derated to 15 lbs. by the refill company they are still not stamped with a new test date. they are still playing Russian roulette with peoples lives.

KingOfHill ~ July 15, 2014

I run a cylinder delivery company. 20lbs is 20 lbs! End of story. There is no secret to it. The cylinder has been engineered to hold 20lbs of propane. The 80% rule applies when it's being engineered, so the tank holding 20lbs of propane is 80% liquid, and 20% vapor. So the contents of the tank weigh 20lbs.

Mary ~ July 23, 2014

I have a propane tank that was never used.

It weighs 38 lbs.
The T.W. is 18 lbs.
I guess that means it's got 20 lbs. of stuff in it.

Edgar ~ August 01, 2014

I have a 20# tank with a TW of 17.7#. It's empty (i.e., no more gas is available when it's connected to my grill), and on a calibrated scale it weighs 18.45#. Any idea what's going on, Jim?

One other thing: I own a number of 20# tanks, all of which have year 2000 date stamps. None have been recertified. What is the risk if I continue to use them?


Jim Ciallella ~ August 31, 2014

Not sure about the different between the tare weight and the actual weight. I don't know if the TW includes the brass valve and the safety float, so that could be the 1/2 lb difference.

I don't believe there is any inherent risk with a tank's age. As long as it's not leaking or very rusty, it should be fine. Though, you might need to get it re-certified before anyone will re-fill it.

I filled big 100# tanks used by welders and tradesmen that were probably 30 years old and banged up but still worked fine. The bigger tanks didn't require re-certification, and probably still don't.

Take care of the tank and keep it from getting wet and it should last. As long as it has the threads on the outside of the valve it should be fillable. The place I went to get a fill yesterday actually had a filler that screwed over the outside threads.

LarryC ~ August 09, 2014

After my first experience with LP, purchasing a 20# empty tank etc. ...
Jim's post here, about 7 weeks back, matches some details I was going to mention too.

I live in San Jose, California ... I purchased an empty tank from my local Home Depot, the brand is BernzOmatic. It was labelled and stickered showing that they come pre-purged for convenience. (Yes, you should tear away the plastic shrink sleeve around the tank, and eventually remove the sticker from the OPD knob saying the tank was pre-purged.)

At my local filling station (which is also a gas/diesel mini-mart) they have a 15 dollar minimum for LP fills, and that was sufficient for my new, empty 20# tank. The storeperson who took care of my fill used a screwdriver blade to turn the bleeder screw, opening the bleed valve briefly, before closing it near the end of the procedure.

The 20# tank is now working in my brand new gas grill. I haven't weighed the filled tank, but I found the experience of purchasing a new, empty tank and having it filled was easy and hassle-free. Thanks for this excellent article, this page is extremely useful.

JerryD ~ August 15, 2014

I am just returning to grilling (after an 8-year stint in an apartment complex that prohibited the use of grills), and suffered sticker-shock when I filled a 20# tank for the first time. After some web research I headed to a Lowed in suburban Philadelphia, and asked the associate about their exchange program; he indicated it would be about $50 for the first tank, and $20 for future exchanges. I opted to buy a new tank and get it filled elsewhere. I bought the tank for $29.99 - the best price for a new tank I could find.- plus PA sales tax of 6%. I then went to the U-Haul I had used previously, and had it filled. Cost: $18.81. I did note the delivery meter was a full 4.7 gallons, so it's priced at exactly $4 per gallon. In the end, I guess I really didn't save much over an exchange. But, I don't think I got ripped off, either. It weighed out at 37# - spot on. Thanks for this article and comment posts - it helped me evaluate the options.

James ~ August 16, 2014

Nice thread lots of great information!

My question is a little bit off topic. I have a Webber Q 1200 grill that takes the small green disposable LP cylinders.

I want to buy an adapter hose for a 20 pound tank. I am not sure if the adapter hose needs to have a regulator on it? I save a couple of bucks if no regulator but its not a big deal to get one if it serves a purpose for this application.

My wife said I have to be safe haha so any help you can give me is much appreciated.


Jim Ciallella ~ August 31, 2014

There are a mix of pictures of the Q 1200 intake. Some appear to have an orange line with a regulator at the end, like

Most likely there's a regulator already somewhere inline. If you have the orange line then leave it as is and screw in the hose/adapter you mentioned.

You'll know if it's not right because it would sound like a jet engine if there's no regulator in the system. I hooked up a line without the proper Weber regulator once and nothing bad happened, it just sputtered and sounded intimidating.

Jim Ciallella ~ August 31, 2014

I just got a fill on a brand new tank. It was pre-purged.

I went to Mobile Bottle Gas in Lyman, SC. The price was posted on a sign as $16, and that's what they said over the phone. It was already the best price I've found in the Upstate of SC, but the lady charged me $12. I didn't ask questions. Maybe that was the price they charged years ago and she had a flashback. Or maybe she knew I was the Google propane guy (doubtful).

The tank was filled with just about 19 pounds, so a very good deal

Visitor5890 ~ September 08, 2014

I have a nominal 20# tank with a TW of 16.6 and a screw-on gauge that indicates empty. This is sort of confirmed by application in that the flame is very weak at the jets of my backyard 'cue. However the tank is still heavy. Based on the above information I use a bathroom scale (first my weight then my weight holding the tank) and this supposedly empty tank weighs 29.2 pounds. I replace the tank with my backup tank and now the gauge reads nearly full but the flame is still very weak. What could be wrong with the tank, the propane, the gauge and/or my barbecue?

Jim Ciallella ~ September 08, 2014

Screw on gauges are not particularly great based on customer returns, but maybe they've improved.

Slow gas may indicate the safety float was somehow triggered. Try turning the tank upside down for 20 seconds and see if that resets the float.

Visitor ~ September 09, 2014

I was just about to go out and by a propane tank and propane when I came across this website. Now I can make the right decision. Thanks!

B ~ September 12, 2014

Thought this was interesting

The Federal Trade Commission issued an administrative complaint against Ferrellgas Partners, L.P and Ferrellgas, L.P. (doing business as Blue Rhino) and UGI Corporation and AmeriGas Partners, L.P. (doing business as AmeriGas Cylinder Exchange), alleging that they illegally coordinated on reducing the amount of propane in their tanks sold to a key customer.

The complaint alleges that, together, Blue Rhino and AmeriGas controlled approximately 80 percent of the market for wholesale propane exchange tanks in the United States. In 2008, Blue Rhino and AmeriGas each decided to implement a price increase by reducing the amount of propane in their exchange tanks from 17 pounds to 15 pounds, without a corresponding reduction in the wholesale price.

“This type of collusion may not be direct or visible to consumers, but can lead to higher prices or lower quality,” said Deborah Feinstein, Director of the FTC’s Bureau of Competition. “So companies should be on notice that when we see this type of conduct, we will take action to stop it.”

VisitorPattie ~ November 01, 2014

I'm an RVr and ran across this excellent thread. In regards to FCC & the 2 biggies collusion in fraud schemes, I feel like I've heard this story before except I've been dealing with the phone and Internet companies lol!

Visitor ~ September 16, 2014

Large metro area 2nd most expensive in the Country , just had 4 20lbs refill , operator bled the tanks and fill them to the max my cost w taxes $65 . all the exchange places from $27 to $21.99 minimum saving $22 maximum saving $43 nice piece of change .... Among the Company they allegedly cheated is wall Mart , now that's hilarious . However Customer can always hire a lawyer and sue Wall Mart they will win .

JimBob ~ September 24, 2014

Do we pay "road" tax on propane ?
I have always wondered if we are paying taxes on propane that we use for our barbequeing purposes, that are more appropriately "motor vehicle fuel taxes". In Canada or in my province at least, the purpose of tax on gasoline and diesel fuel for motor vehicle was to maintain highways and pay for other forms of transportation. When I was an accountant in the logging business (a few years ago), it was common practice to get a rebate of all fuel taxes for vehicles uses "off highway" i.e. in the bush. You got a rebate on all that fuel tax you paid for the big trucks, when those trucks were used in the bush to haul logs, or crews or whatever. Mileage was calculated on daily trips, and the rebates were huge. So when we fill our propane tanks at the local dispensary (where they are probably fueling autos also), are we inadvertently paying a tax that we shouldn't be ? Our barbeque is never going to be racing up and down Main Street. Are we paying the "road" tax on that fuel that we shouldn't be ? Perhaps the local business knows that and gets the rebate as part of their profit (if they have a separate dispenser for propane) ??
Just curious.

SD ~ September 26, 2014


Here in the states, Texas specifically, propane does not have a road tax associated at point of sell. For automotive use, a propane decal is purchased annually. Purchase amount depends on estimated number of miles to be driven (if new), or based on number of miles driven in past years (if renewing). Mileage is reported.

Automotive / ACME tanks are not readily seperable from the vehicle, and typically use a different type of fill connection. That being said, most propane pickups and vans also have ability to use portable DOT cylinders in case of an 'outrage condition' in emergency situation. Such as running out of LP during rush hour and stalled in roadway.

I am not sure how road tax is calculated on bi-fuel vehicles, or those that warm up on gasoline and switch to propane automatically. Perhaps gasoline road tax (paid at pump) is refunded altogether when propane purchase volume correlates with mileage driven.

Tom Sellers ~ September 29, 2014

Great article and comments. I've recently realized that to get around the problem of my 20lb roof tanks outside on the van giving up at -25C when they are half full, I'm better off to refill the 1lb bottles and use them (observing all the proper precautions of course) where either the ambient air temp, or prewarming in warm water, allows them to work better. With your inquiring mind and great writing style, I wish you were into the topic of winter backpacking stoves and refilling butane/propane mix canisters.

Visitor ~ October 02, 2014

FYI...I had 2 old tanks...U-haul wouldn't refill them. (If they're 10 years old, they have to be re-certified.) So, I took them to a Blue Rhino propane exchange and they swapped them out for new (certified) propane tanks. So, they might have ripped me a little in that I didn't get my full 20 pounds, but I stuck them a little by giving them tanks that no propane refiller would touch. ;)

San Diego ~ October 12, 2014

In Southern California Costco charges by how much they put in not a 20lb flat rate. Every time I go the amount their machine auto fills to is different based on the temperature at the time of fill. But again, Costco in my area charges based on how much they put in your tank. Usually cost around $7.50 to 8 dollars to fill a 20lb tank.

S G ~ October 23, 2014

The original post indicated that the weight of a full tank should be 37 pounds with a TR +17 stamp. My recently filled cylinder weighed 37 pounds, however empty it weighed 23.7 pounds which means that only 13.3 pounds of propane were introduced into my refilled tank....correct? The U-Haul I took it to charged me for 4.25 gallons at $3.92/gallon. The weight of 4.25 gallons should be 17.85 pounds (4.2pounds/gallon). If my cylinder weighed 23.7 empty then it should weigh 41.55 pounds with the 4.25 gallons added. From what I can tell U-Haul is shorting my case almost an entire gallon. Since they are charging me $3.92/gallon, they just screwed me out of that amount on a refill. They stated that they didn't have to fill by weight in North Carolina. My suspicion is that the gauge is incorrectly set. One has no recourse except to pay, although it is still cheaper than buying a tank down at Ace (trade in) at $25.00.

Jim ~ October 24, 2014

I've never heard of an empty tank weighing 23 lbs, so that's probably part of the discrepancy. The real empty weight is stamped as TW on the collar.

Visitor ~ October 24, 2014

I solved this problem earlier this year after going through a fair number of charcoal and gas grills over the decades. Paid a fortune and bought an XL Big Green Egg. Wife does most of the grilling because she likes it, while I'm skilled at opening the patio door, carrying stuff, using the grill brush, and observing her talents while I enjoy a well-deserved adult beverage. She loves her Egg....and I love her great food.

Visitor ~ October 29, 2014

I'm really glad someone brought up the exchange places. I'm a propane retailer that can only fill up tanks less than 12 years old and use the bleeder valve on a set of scales. We weigh each tank. If we fill an old tank and get caught we are fined heavily and lose our right to retail propane. The exchangers who are the big boys only fill to 15lbs its printed in small print on the plastic wrapper on the tank. These guys also use outdated tanks I wish the state would check them but it appears they operate with impunity. Most of us retailers work hard and try to make a fair not indecent profit. It's the exchangers who are really ripping off the public.

Rob ~ November 03, 2014

Stumbled onto this while searching for info on propane fills.

I think something has changed at Costo in Greenville, as I filled two 30# tanks there last week (October of 2014): It was sold to me by the gallon, and I paid after the tanks were filled.

condew ~ November 04, 2014

A few years ago I was helping a friend keep a shed warm using 20lb tanks day and night. The tanks were out in Winter temperatures and we were drawing propane to create about 6000 BTU of heat. After a while we had problems with a lot of oil in the lines; either put in the tank by sloppy maintenance at the filling station, or by drawing lots of propane at low temperatures, maybe we distilled out an oily fraction of the propane. If your tank has a pound or two of oil in it, it makes all the calculations about how much propane a tank should hold and how much propane you got for your money an even more complicated question. I didn't know about the stamped on tare weight, but comparing the weight of an empty tank to it's tare weight would have been a way to detect this problem.

Steve P ~ November 28, 2014

Yep, I saw at the Blue Rhino exchange yesterday a sign that say "Net Weight 15 lbs." which is why I searched to find out how much the tank weighs. Thanks for the info. Awesome. This is why we have the Internet, Jimmay!

bonobos marcos ~ December 04, 2014

Wow thanks for the information! I can remember being in high school and having my baseball team come over every week for my dads grilled hamburgers. I guess you could say we went through alot of propane. He always kept it refilled though and sometimes had me do it!

Visitor ~ December 11, 2014

Hmm as gas prices decline....12 bucks at 4 gallon of propane.....thats 3 bucks a gallon...thats way to high of a price....screw

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