Wednesday, November 29, 2023


Save money: Recertify propane cylinders

By Russ and Tiña De Maris
Do you remember the story we ran about motorhome owners getting the runaround when trying to fill their propane tanks? Many wrote in and shared how they had been told by propane pump jockeys that their tanks were “out of date” and couldn’t be filled. We also heard from plenty of towable RVers who told us their horror stories about trying to get their LP cylinders refilled. There’s plenty of misinformation out there, and we’ll try to clear it up. You can save money if you recertify propane cylinders, instead of buying new.

Tanks versus cylinders

First, let’s clarify some terms. Motorhomes, as a rule, have propane “tanks” that aren’t easily removed. They’re typically bolted to the chassis, and you have to drive them to a station to get them refilled. If your motorhome was manufactured in the U.S., the tank will be stamped ASME, meaning the tank is certified by the American Society of Mechanical Engineers. Under U.S. law, your tanks DO NOT need to be “re-qualified” or “recertified” – they don’t “date out.” You may not be able to convince an overzealous propane pump jockey of this, but those are the facts.

On the other hand, the typical towable unit, be it a fifth-wheel, travel trailer, or pop-up, has a propane container that is easily removable. These are the ones you can take away from the rig and transport them for refilling. You’ll know them when you look at the collar or “neckring” that protects the valve. Stamped on the collar will be the legend “DOT” – which stands for the U.S. Department of Transportation. These containers are not “tanks” – they are technically cylinders. Their sidewalls and bottoms are made of thinner metal than a motorhome tank, and they’re more susceptible to damage.

How often must they be recertified?

Under federal law, all DOT cylinders MUST be periodically inspected and requalified. The rule is somewhat muddy. Most recently the Department of Transportation indicated these cylinders needed to be requalified or recertified 12 years after their date of manufacture. Here’s where the mud comes in. Initially, the agency proposed these would need to be recertified at the 10-year mark after manufacture. But when the final rule came out, it was 12 years. Some propane pumpers are under the impression that the critical date is 10, not the actual 12. Again, you may find it difficult to convince them. Adding more misery, some LP cylinder manufacturers stamped that their products must be recertified in 10 years. Go figure.

Click to enlarge

So, how do you know when it’s time to recertify a propane cylinder? The answer is on the collar. If you check out the diagram, you’ll see an item labeled “F”. Stamped on the neckring in that location are four digits. A two-digit month, and a two-digit year. In our example, this LP cylinder was manufactured in April 1994. Add 12 years, and you’d know this cylinder was “up for recert” in April 2006. If you tried to get it filled today, you should be told that it (rightly) can’t be refilled – “it’s out of date.”

Toss down that credit card!

We heard from many readers who told us that when they were told their cylinders were past date, they simply threw down their credit cards and bought new ones. That’s probably just peachy for a lot of propane filling outfits. In addition to the profit they make on selling you a new cylinder, many of such cylinders will need to be “purged” for an additional charge. Purging is the process where the propane retailer removes the air from a new cylinder. Then, to top it off, there’s the “fill ‘er up” money to be made.

Dates around the collar

Stamped date – visually inspected (E) March 2020. R&T DeMaris photo. Click to enlarge.

But we’ve already talked about requalifying an LP cylinder. Back to the diagram. Where the pointer from the “G” legend is, on our sample collar you see the word “Retest.” You won’t find that on any cylinder we know of. BUT there may be a date code, because this is the area of the cylinder where a qualified inspector can stamp (or stick on a label) with the information that the cylinder is still safe for use. What might that look like?

The most common requalification code will have a 4-digit date code, followed by an “E”. This E indicates the cylinder was visually inspected. Another possible letter, in addition to the date code, is “S” for proof-pressure inspection. Finally, a date code with no letter following indicates a volumetric expansion test has been done.

What does this all mean?

Certification seal, E on right signifies visually inspected. R&T DeMaris photo. Click to enlarge.

To recertify a propane cylinder, the qualified inspector can use any of these methods. The quickest, easiest, and least expensive test is simply a visual inspection of the cylinder. If an E is stamped, that means the next requalification must be done within five years of the date. An S designation or no letter at all, for the other two methods of inspection, means the cylinder is good for another 10 years before needing another requalification.

It’s best to note, those recertification stamps may appear elsewhere on the collar. In one instance, a “newbie” inspector stamped the recert code right into the top of our cylinder, rather than on the collar. A bit dangerous, as the metal there is pretty thin! Sometimes an inspector will use a sticky seal. They’re a lot easier to read.

Recertification costs

What’s best – an inspection leading to re-qualification, or a new cylinder? We called around the country, from the Midwest, down to Texas, and over to Arizona. We checked with different companies, and here’s what we found in terms of recertification costs. Every inspector we found was associated with a propane refill station. Some would simply give you the inspection for free, provided you filled up your cylinder when the inspection was complete. A five-dollar fee was the next most common. Some asked a “tenner,” but the highest rate quoted was in Quartzsite, Arizona, where one oufit charges $35 for a recertification inspection.

Will your cylinder pass or fail?

What does an inspector look for? Damage to the cylinder. Those would be dents, bulges, cuts, or cracks. They’re also looking for evidence of abuse – fire and heat damage, or welding done to the container. “Detrimental rust, corrosion, or pitting” says the DOT is a definite no-no, “particularly on the bottom.” If the neckring is missing, or the footring at the bottom, it’s an automatic “fail.” Finally, if the valve or pressure relief device leaks, your cylinder won’t pass. While there’s nothing much to be done about many of the “rejects” here, a leaking valve is not necessarily a death sentence.

Leaky LP valves are easily replaced

The typical cost we were quoted was $35. The highest was $40 (including the recertification charge), and the lowest, $24.95. How does that stack up against the cost of a new cylinder? Camping World will happily sell you a 30 pound (7 gallon) cylinder for $103. Amazon carries them ranging in price from $67 to $107. We replaced a badly damaged LP cylinder with an Amazon purchase. It came with free shipping, and didn’t require purging – the factory issued the new one with, not air, but a vacuum, inside. We have had several cylinders requalified and have saved plenty of money. We do paint them with white spray enamel as needed, but it’s cheap and easy.

How do you find an outfit that’s qualified to recertify your LP cylinder? We found it easiest to simply call RV part retailers and ask them who in the area could the job. It was much faster than calling a multitude of propane retailers to ferret out the few that do recerts. Bottom line: Save money. Don’t buy a new if you don’t need to. Recertify propane cylinders and put the savings elsewhere.


Turned down when you want propane? For some RVers, it’s happening
For more stories from Russ and Tiña, click here. 


Russ and Tiña De Maris
Russ and Tiña De Maris
Russ and Tiña went from childhood tent camping to RVing in the 1980s when the ground got too hard. They've been tutored in the ways of RVing (and RV repair) by a series of rigs, from truck campers, to a fifth-wheel, and several travel trailers. In addition to writing scores of articles on RVing topics, they've also taught college classes for folks new to RVing. They authored the book, RV Boondocking Basics.



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Garth McElree (@guest_155256)
1 year ago

Just finished a trip from Ontario to BC and back in Canada with a 2006 Class A motorhome with an ASME propane tank. Propane refillers routinely checked for the recertification sticker in the front window and/or the brass tag attached to the tank. They have apparently been trained to look for them and not to fill a tank if a recertification has not been done. Probably easier than to teach them to look for the certification than how to visually inspect every tank before refilling. I have seen a few ASME tanks that failed recertification and the rust damage was really bad. Certainly they are built better and stronger than DOT tanks but nothing lasts forever given the amount of salt we use on our roads around here.

Recent increases in cost of replacement parts has made repair of 20 lb DOT tanks virtually uneconomical at this time. However, there are still substantial savings to be achieved repairing/recertifying 30lb, 40lb and larger tanks.

Good article.

Drew (@guest_155045)
1 year ago

I’ve only had one guy ever look at my tanks.

Sally Harnish (@guest_154797)
1 year ago

Something to remember. If going to or thru Canada and going to refill recertified tanks in Canada, they do not accept US recertification.

Drew (@guest_155046)
1 year ago
Reply to  Sally Harnish

Can’t they read up there?:)

wayne (@guest_154745)
1 year ago

Why not just take your expired empty tank to any place that swaps out empties for full certified ones?

H Goff (@guest_154813)
1 year ago
Reply to  wayne

Duh – that was what i was thinking – not sure if the author is aware of that. Most of the time you’ll get a tank that has several years left on it – then you can take it to the re-filling station the next time. In general, there is only a few bucks difference between swapping and filling. It costs $8 here to recertify – so I could exchange twice before breaking even.

Tommy Molnar (@guest_154835)
1 year ago
Reply to  wayne

I’ve never seen a swapout for RV sized propane tanks. You usually get this for bbq sized tanks. We just recently did this and looked through all the available tanks to find the newest one. Now we’re set for another nine years with our bbg.

MrDisaster (@guest_154900)
1 year ago
Reply to  wayne

The propane exchange facilities only handle the smaller “5” gallon (20lbs) size tank. So it wouldn’t work for the larger “7” gallon (30 lbs) tanks.

Thomas D (@guest_154743)
1 year ago

Some rules make no sense. When i had a motorhome the tank was so very rusty. It even scared me. No problem. Its good. A tank in my fiver that never saw the light of day needed to be recertified or replaced. It looked new. Now I have a 5 gal tank and if i decide to get a different tank I can go just about anywhere and get a tank already filled although they only put in 3 1/2 gallons.

Phil Atterbery (@guest_154737)
1 year ago

I’ve encountered folks that know enough about propane to be dangerous. I don’t go back. I’m not going to retrain the operator. I will call the local distributor of the fill station and ask them to correct the operators methods.

Bill N Stacey (@guest_154736)
1 year ago

I had a VERY hard time finding anyone in the entire state of Florida! After sugnificant research (also calling RV dealers)… I only found one place in Miami.. This is not a common service anymore! Its a “Disposable” mentality today.. Uggh

John (@guest_154722)
1 year ago

Re certifying cylinders was 10 bucks apiece. I think it was for 5 years . Don’t have them anymore so I couldn’t check. Alot cheaper than buying new.

Tom (@guest_154721)
1 year ago

Well, this article does little to clear up any confusion about when tanks need to be recertified. In the upper section of the article, it states that there “is confusion” on whether tanks need to be recertified after 10 or 12 years, then appears to clear the issue with, “…when the final rule came out, it was 12 years. Some propane pumpers are under the impression that the critical date is 10, not the actual 12. Again, you may find it difficult to convince them. Adding more misery, some LP cylinder manufacturers stamped that their products must be recertified in 10 years. Go figure.”

This is immediately followed by a diagram that explains what the different notations on the tank represent. Under bullet “G”, it states that the recertification date is blank, indicating that “the 10-year recertification is overdue”.

Hmm, go figure.

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