The Truth About Filling 20 LB BBQ Grill Propane Tanks

Posted 1 year ago by Jim Ciallella

A public service announcement, in time for football season, about filling propane tanks, propane at Costco, and the quality of Weber grills.

Background

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). Now, where to fill it?

A Little About Propane Tanks

These "20 lb" tanks are designed to take 20 pounds of propane. They can actually fit another 20% in the tank, but that extra space is designed for expansion as the temperature changes.

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 come with air inside and it needs to be "purged" before the first fill. 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.

Conclusion

  • 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

23 Comments

Evan Tishuk ~ 1 year ago

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

Chip Nimmons ~ 1 year ago

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 ~ 1 year ago

Side burners are great for frying things!

C-Town ~ 1 year ago

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 ~ 1 year ago

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 ~ 1 year ago

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 location....no 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 ~ 1 year ago

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 ~ 1 year ago

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.

Visitor ~ 1 year ago

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

Another Visitor ~ 1 year ago

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 ~ 1 year ago

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 ~ 1 year ago

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 ~ 1 year ago

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 ~ 1 year ago

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 ~ 1 year ago

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.

dhgasman ~ 1 year ago

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 ~ 48 weeks ago

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 ~ 48 weeks ago

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 ~ 48 weeks ago

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.

Marlene

Jim Ciallella ~ 48 weeks ago

Visitor (with the frozen tank),

UPDATED

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. http://www.propane101.com/propaneregulatorfreezing.htm

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.

Marlene,
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 ~ 47 weeks ago

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 ~ 46 weeks ago

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 ~ 46 weeks ago

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.

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