Quick Summary

My recommendation:  Refill your tank, unless it is out of date (and cannot be legally refilled without recertification).
If it is out of date, exchange it. Make sure you get one that can be refilled.

Major point: Exchange services under fill the tanks to only 15 lbs. rather than the about 20 lbs that they will safely hold. Refilling gives you the full capacity.

Refilling and exchanging

It used to be that taking your gas barbeque’s propane tank to a local refilling station was the only option. Then the exchange services came along, initially at some hardware stores, but now at a variety of stores. The exchange services made it quick and easy to get a full tank of gas. The prices varied, but were generally higher than then refilling, but not by a lot.

The exchange services brought several advantages to stores. It was now easy for a store to get into an additional business with little hassle. The cages of propane sit locked outside of the store, not taking any precious in-store shelf space. There was no need to have a large tank installed in the parking lot somewhere. There was no need to have employees trained and certified in the filling of tanks or to have an employee tied up for 10 minutes at a time filling tanks. When someone comes to exchange a tank, they are also likely to purchase other items. It gives them a reason to visit the store. A propane company handles the inventory of full and empty tanks. For the store it is additional business and profit. What's not to love?

For the customer it is also quick and convenient. Filling a tank sometimes requires waiting a bit for the employee who is trained to become available to fill the tank. You don’t have to worry about your tank being out of date. The exchange places will take the out of date tank (generally even if they do bother to check) because the propane companies can easily recertify the tank.

A 20 lb propane tank about to be refilled.

Disadvantages of Exchanging
There are some major disadvantages to the tank exchange, and most of them are not so obvious:

Exchanging a partially full tank.

If you only have one tank for your grill, you probably do not want to have it run completely out before exchanging or refilling. Do you really want a half cooked steak? Many a family BBQ has been interrupted by a quick trip to get more propane. That is if you can find some place open.

So the smart thing to do (if you only have one tank) is to fill or exchange the tank before it is empty. Not an easy thing to do as it can be hard to judge. So you may be doing so with 5 pounds left in the tank.
If you refill, you then simply add 15 pounds or so to the tank and pay for what you added. If you exchange, you are giving the propane company 5 pounds of propane and paying for the complete exchange.

You will likely pay more for the exchange, even if your tank is completely empty. An empty 20 lb tank will hold about 4.7 gallons of propane. That is $18.47 at $3.93 per gallon, which is the low quantity price (I just paid $3.44 per gallon when filling several tanks). The exchange is about the same price. Keep in mind this comparison is as if the exchange gives you a FULL tank. A lead in for….

The worst and most devious problem: Under filled tanks.

Virtually all of the tank exchange companies now only fill your tank to 15 lbs. They apparently started doing this when the price of propane went up with gas prices several years ago. This saved the propane companies money. They claimed that they were doing an incredible service to customers by not having to raise the price. Pure marketing BS. After complaints, they do now list that the tanks are filled to 15 lbs, but very few people are going to realize this. They try to sell it as a feature. “Tanks filled to 15 lbs!!!! Wow!!!” Ask 20 people who exchange a tank, and I’ll bet 18 of them don’t realize that the tank is under filled, even if they do read the “notice”. That would be like going to a gas station and having the attendant (OK, so there aren’t any attendants anymore) tell you that they have not raised the price, they will just fill your tank to ¾ full for the same total price as they previously filled it to the top. OK, ice cream and coffee companies have done this, but they made the package smaller also. For propane, you really can’t see how empty it is.

The price of propane went back down. Did they go back to refilling the tanks to 20 lbs? No, they are still at 15 lbs. No company will be the first to go back to full because they know that the very few consumers would notice and it would put them at a competitive price disadvantage.

A store or company may try to tell you that the 20 lb cylinder can only hold 15 pounds because they cannot be filled all the way up due to safety.  They are double counting.  With the full 20 lbs there is still about 20% space left for expansion.  The "20 lbs" already takes this into account.  I have seen many people online incorrectly make the argument that a 20 lb tank can only safely hold 16 lbs of propane.

Why is the under filling a problem:

• Consumers do not realize that they are getting only a ¾ full tank. Even when it does say “filled to 15 lb”.
• The tank runs out quicker requiring more trips to the store.
• You pay a price for the convenience of the exchange. You now pay that price more often.
• If you have just one tank and return it with 5 lbs left to avoid running out, you are now getting a higher percentage yet of waste. The propane company only has to add 10 lbs to your tank when they refill and sell to someone else.
   

What is next? 12 lbs? 10 lbs? I’m sure they can come up with a very good reason to do so. Note that even before dropping to 15 lbs, many tank exchange places were only filling to 17 lbs. Companies are in business to make money, pure and simple. This is a technique to make more money that the customer rarely notices, but definitely pays for. So expect the amount to continue to go down.

Refilling – the good and the bad.

As you can see I highly prefer to refill. It is cheaper and you get a full tank. But there are a few issues there also.

• There are fewer places that refill now, and their hours may be limited.
• You may have to wait for the trained employee to become available. Having to wait a bit longer is worth it if you don’t have to come back as often.
• There is a little bit of waste when refilling and you pay for that. This comes from two places:

• The bleeder valve is opened when filling allowing some gas to escape, and a bit of liquid when full.

• When the tank is full there is some liquid in the nozzle that is wasted.

• Neither of these amounts to very much. Well under a pound.

Some places charge by the tank, not by the gallon.  There is a disadvantage here if you are refilling a tank that is not empty.  You should also make sure that they will be filling the tank to the full capacity.  For price comparisons between per gallon and per tank charges, consider that an empty 20# tank will hold about 4.6 to 4.7 gallons.  To keep the math simple (if doing it in your head) consider 5 gallons times the per gallon price and subtract about a dollar.

Where to refill? Some gas stations. Most U-Haul dealers. Commercial propane distributors (who also fill large tanks with delivery trucks).

Recommendation

Refilling is generally the way to go, but always compare prices.  A tank exchange with 15 pounds contains about 3.53 gallons of propane.

Use the tank exchange when your tank is out of certification and cannot be refilled. Getting your tank recertified is not practical. I’m not even sure how you would go about doing this. You could buy a new tank, but you can just exchange the existing one. Check that you are getting a tank that is not close to its recertification date (12 years after the date stamped at the top). That way you can refill it later. The propane exchange company will simply recertify your old tank and reuse it. They have people that can do that and it is very cheap for them due to their volume.  It probably takes them 15 seconds.
If you do refill a tank that you previously got from an exchange, you may want to remove their shrink wrap advertising wrapper, although there is no need to on your part. Besides advertisement the main purpose for this wrapper is to hide rust on the tank. Notice that the plastic is NOT clear, it is mostly white.

Buy a spare tank. That way you can run your tank empty before refilling or exchanging, knowing that you have a spare to finish cooking that expensive steak. It will cost you about $20 to $25 up front, but you may save in the long run and will not run out in the middle of the BBQ.

I have a total of 8 tanks. There are several reasons for this: 1) I have multiple propane appliances including propane heaters and an outdoor fireplace. 2) I bought some new tanks when the OPD valves became a requirement, not realizing that I could exchange the old tanks for ones with the OPD values. I later exchanged them.

When you buy a new empty tank, the person filling it will have to purge the air from it first. They seem to consider that a real pain, and will often charge you $5 or so for it. The tank initially contains air, which will not compress to a liquid at anywhere near the pressure that propane will. If the air is left in you will not be able to get very much propane in the cylinder. The process takes several minutes, and wastes a little propane, but it is necessary.  What they do is add some liquid propane, then open the bleeder valve to let out the air.  Some propane vapor will also escape at that time.

Price Comparison

Since you have to come back more often with the ¾ full tanks, the exchange cost is $24.62 for an equivalent amount of propane. Substitute that number in all rows of the exchange.

I have nothing against the tank exchange companies.  They have found a new business model that works for them and certainly has some consumer benefits, often at a price.  Nothing wrong with that at all.  I do not care for the practice of only filling the tanks to 15 lbs, even if they do clearly label it.  Legal?  Probably.  For me, it doesn't pass the smell test, however.  The label should say "This 20 lb tank is only filled to 15 lbs for our benefit, not yours".  Again, 90% or more of people have no idea they are getting a partially filled tank.  If the propane exchange companies filled the tanks to the (near) 20 lb full, safe limit, I would have never written this web page.

I welcome rebuttals.  But stick to the facts.  Don't call me an idiot because I used incorrect grammar somewhere.  I have a wife for that.

Blue Rhino TS2 tanks.

Update: I do not know if these still exist.  I have not seem them locally, and most online discussions on them seem pretty old.

Blue Rhino apparently has their own proprietary “TS2” valve. The purpose of this is to prevent you from refilling one of those cylinders at your local propane refiller. The tank can only be refilled by them due to some sort of magnetic interlock, for which they have the key.

They claim that this is for “your safety”. I.E. they are the only people in the world who can safely fill a propane tank. They will try to play the safety card. It is Bogus. The TS2 provides no other “safety” than preventing others from refilling.  This is NOT the same is the Overfill Protection Device (OPD) which has been required for all tanks for quite some time now.

The real purpose is two fold (they will have a different spin on this, I’m sure):

To force you to do a tank exchange with them instead of refilling. This is 99% of the reason.

To reduce their theoretical liability a tiny tiny tiny bit. I.E. if you have a Blue Rhino tank that you then have refilled, and something later goes wrong, they don’t want you to come back and complain to them. Their thought: The refiller may overfill or do something else wrong and then you (the customer) claim it was Blue Rhino who did it not the refiller. In reality the OPD prevents the overfilling, and if that fails, the bleeder valve tells them (and you while you watch) that the tank is full.
Just an excuse by corporate lawyers to put in something that will prevent you from saving money.

They claim that some of their tanks do not have the TS2 valve. I have read that it varies by distributor.  I have asked the place where I refill and was told that they have never come across one that they could not fill.  Apparently there is a triangular indentation on the value itself on the TS2 valves (not to be confused with the triangular valve handle that you turn, which is on ALL newer tanks).

By the way, you OWN the cylinder. You are not borrowing it from them, so you have the right to do what you want. If you get a full cylinder without bringing in an exchange, you pay extra to buy the tank (generally $25 – about what you would pay in a store for a brand new tank).

Would you buy a car that has a special gas cap “for your safety” that can only be filled by the car dealer’s gas stations? “Not everyone can properly fill a car with gas. We’re doing this for your safety.”  After all, some people do top off.

About propane tanks.

The standard BBQ tank is generally referred to as a 20 lb tank as that is the amount of propane that it will safely hold. Some might hold slightly less than this as the OPD valve varies in size, but it is well over 19 lbs.

The tank is NOT filled all the way to the top with liquid. It is only filled to about 80% of the volume. That is for safety purposes. When filled the tank often gets cold due to some evaporation of the liquid. If the tank is then left out in the sun the liquid would expand. If all goes well, the safety pressure value would vent the excess liquid. This would be somewhat of a safety problem as you have escaping highly flammable gas. However, if the safety value was not functional, the tank could, under extreme conditions, rupture causing an extreme safety hazard. Filling to 80% allows for the expansion without any venting of gas.  The full 20 lb (or nearly that) already takes into account the 80% fill limit. Don’t let anyone tell you that the real limit is 16 lb. Someone selling you a tank filled to 15 lb will try to tell you that. They are wrong.

The OPD valve is there to prevent accidental overfilling of the tank. With thousands of people filling these tanks, some would do it incorrectly and overfill them, causing the safety hazard mentioned above. The OPD value prevents this by using a float sort of like a toilet tank float (there are multiple types, just like toilet floats). It is a good idea. The shut off valve handle is in a triangle shape if it has an OPD valve. Old ones were various shapes. You will only see one of those if you have a very old tank.  The OPD requirements took affect as follows:  "New cylinders for vapor service which are fabricated after September 30, 1998; as cylinders are requalified after September 30, 1998 through March 31, 2002; effective April 1, 2002, before a cylinder is filled."  The requirement is for tanks 4 to 40 lbs.

Tank Markings

The followings markings are found on the tank:

TW: Tare Weight. The weight of the tank when empty. Very useful when weighing a tank to determine how much propane is left.  Typical values for a 20 lb tank are 16.6 lbs, 17 lbs, and 18 lbs.

WC: Water Capacity. The capacity of the tank in pounds of water. This is to the very top. Typical tanks are 47.1, 47.6, or 47.8.  47.8, when divided by 8.34 lbs per gallon is 5.73 gallons. 80% of this is about 4.6 gallons which is as much propane as can be put in.  Propane weighs about 4.24 lb per gallon, so 4.6 gallons is 19.44 lbs. Charts generally indicate that 47.8 lbs WC can be filled with 20 lbs of propane.

DT: Dip Tube. The length of the dip tube, which is where the bleeder value opening inside of the tank is located. This determines how full the tank will get before liquid starts coming out of the bleeder valve, when open. Typical values are 3.8 or 4.0 inches.

How to tell how much propane is in the tank:

One way to tell how much propane is in the tank is to weigh it.  You can use your bathroom scale to weigh the tank, then subtract the Tare Weight, which is stamped metal piece that is welded to the tank.  Tare weights are typically 16.6 to 18 lbs.

Bathroom scales are not the most accurate things in the world, so caution is in order.  You can calibrate somewhat by weighing the tank when you know it is empty.  Write this weight on the tank for future use when you weigh with the same scale.  You can also weight when full (if it is your only tank and never run it empty) then subtract 20 lbs (if you had it filled).  This is less accurate, as you are not sure there is exactly 20 lbs of propane in the tank.

In any case, weighing will probably give you a better indication than your average car's gas gauge will.  I have one vehicle which sticks on Full for a long time then quickly drops.  My new car has an 18.5 gallon tank, but the gas gauge and the electronic "range left" indicator thinks it will run out after using only 13 or 14 gallons.

Interesting tidbits:

Ebbetts Pass Gas. Yes that is the real name of the propane company in Arnold, California (near Ebbetts Pass).

On the TV show “King of the Hill”, Hank Hill works for a company that sells “Propane and propane accessories”.

Using 1 lb disposable cylinders for camping.

The 1 lb cylinders are convenient, but they are not refillable. They end up in the landfill. Cost wise, it depends. If you use a 20 lb tank for camping, you may end up buying a $30 distribution post and $15 hoses. The return on investment may require you to use greater than 20 one pound cylinders. If you don’t camp very often, the 1 lb cylinders may well be the way to go.

The 1 lb cylinders are convenient. The propane lamp is portable. They don't take up much space in the trunk. They are necessary for some items, such as the catalytic heaters, in which the cylinder is part of the physical support.

The 20 lb tank is bulky and takes up a lot of space in the trunk or back of the mini-van. They do make smaller tanks in the 10 lb or so size, but these are EXTREMELY expensive. $60 to $80 or more vs. the $20 to $25 for the 20 lb tank.

I personally use both. I use a 20 lb tank with a distribution post to which I attach my lantern and stove. I also bring some 1 lb tanks for use when I need portability or multiple locations.

My first distribution post leaked from every possible point. Not from the valves themselves, but from the connection of the brass valve to the metal tube. One spot had a leak large enough to smell at a distance. The others failed the soap test. The US Consumer Product Safety Commission now has possession of that one (they reimbursed me for it). My second one works fine (update: the plastic connection to the tank cracked, so it is now useless).

I have also had 1 lb cylinders leak, however.  After disconnecting them from the stove/lantern, I could hear hissing of the escaping gas.  I certainly didn't want to put that one back in the car!!!  Fortunately it was early enough in the camping trip to just keep it attached to something, and I used it up.

There are "Refill Adapters" available to refill the disposable 1 lb cylinders from a 20 lb tank.  Personally I consider this to be quite dangerous and would not try this.  Some of the reasons:

• There is no overfill protection on the 1lb cylinders and you are could over fill them.
• The valves on the disposable tanks are not robust and likely to leak with multiple uses (some of the instructions tell you to poke at the valve with a nail to stop the leaking).  There is not a second manual valve on these like there is on the 20 lb cylinders.
• It requires you to invert the 20lb cylinder to have liquid propane flow to the 1 lb cylinder.  The tanks are not designed for this.
• Instructions for these warn of the tanks freezing up and suggest wearing gloves to prevent frost burns.  Not a good sign.
• The tanks have the following warning:  "Never refill this cylinder.  Refilling may cause explosion.  Federal law forbids transportation if refilled - penalty up to $500,000 fine and 5 years imprisonment (49U.S.C. 5124)."  I have two different brands with the exact same wording.

There is a company that makes refillable 1 lb cylinders.  They are refilled from a fork lift propane tank, which is designed to deliver liquid propane.  Purchasing a fork lift tank (if you are like me you probably don't have one) makes it expensive, however.  It would require a lot of refills to break even.