In the United States, the propane tanks on the tongue of your vintage trailer are called DOT cylinders. That's because they meet the standards of the US Department of Transportation to be portable. In Canada they are called TC cylinders for the same reason.
The aluminum propane tanks we sell are DOT and TC approved. In the United states, DOT rules apply to their ongoing safety too.
In accordance with DOT rules, every time your tank is filled, it gets an inspection. The technician is not allowed to fill your tank if they notice any of these issues:
- Damage to the cylinder’s exterior including dents; bulges; cuts; or cracks on the cylinder’s surface, or to welds; and any evidence of physical abuse; fire; or heat damage.
- Detrimental rust, corrosion, or pitting on the cylinder, particularly on the bottom.
- Absence of/damage to a cylinder footring, cylinder neckring (collar), or valve cover.
- A leaking or defective valve or leaking or defective pressure relief device.
Assuming your tank passes the above inspection, the technician will then look for a date on the tank. Portable DOT/TC tanks do not expire. But they do require inspection and requalification over time. If a tank is not up to date, it cannot be filled.
When propane tanks are made, they are stamped on the collar with a bunch of numbers and letters that indicate everything from the tare weight (TW) to the length of the valve's dip tube (DT). Among those stampings is the manufacturing date shown as just month and year, like 08-97.
In the United States, a tank can be used for 12 years from the date of manufacture before it must be requalified (sometimes called recertification). In Canada, the tank can be used for 10 years before it must be requalified.
Requalification is a simple process done by a trained technician. You'll pay to have the tanks inspected and requalified. With steel tanks, that may not be worth it because steel tanks rust and they aren't very expensive in the first place.
But with aluminum tanks, it is well worth the cost of requalification. With just a little care, aluminum tanks will last a lifetime. We see aluminum tanks from the 1970s safely still in service on vintage Airstreams.
When your tank is requalified, you will either get a sticker on your tank or another date inscribed into the collar. If the collar gets a new date, it will have a letter after the date. Normally, that's the letter E. E means the tank was externally inspected.
In the United States, that new date with the letter E will give you an additional 5 years to use your tank before it needs to be inspected and requalified again. You can continue to requalify a tank as many times as you like, as long as it remains in good condition.
To be clear, if the date on your tank does not have a letter after it, you are looking at the original manufacture date so you are good to go up to 12 years from that date.
The dates and their letter codes make it easy to see the history of your tank and let you know how to get it ready for the camping season.
- If your tank is a more recently manufactured DOT 4-series tank, it has a 10-year requalification option. It costs a bit more because it will be a hydrostatic testing process. 4-series tanks are labeled with a 4B or 4E or some other 4 code. If you see that on your tank collar, ask your technician if that option is available.
- The aluminum tanks we sell are TC certified as well as DOT certified. TC is for Transportation Canada. TC rules are different than DOT rules. In Canada, the initial qualification and all subsequent qualifications are good for 10 years.