Does Propane Go Bad?

Last year you filled your propane tank on your RV. You're getting ready to hit the road and need to know if it's still okay to use. There's more to it than just an expiration date, let's dig into the details.

What is propane?

I'm tempted to dive into chemistry equations to show how propane really works at a molecular level, but I'm afraid that might scare some people off.

Propane gas is an energy source because it can burn easily. It can be used in engines in a similar manner as diesel fuel, It is also very common for heating applications.

Propane is obtained in two ways. Raw petroleum gas is separated into natural gas and propane (as well as other fuel sources). Crude oil is distilled and propane is one of the energy sources split up in the process.

Liquid propane is often called LP, and you'll probably hear it called LP gas. It's certainly confusing to call something liquid propane gas, but it all has to do with pressure.

At our standard atmospheric pressure propane is a gas. Its gaseous form takes up a lot of space, so we compress it and store it as a liquid for convenience.

As long as it stays at that high pressure, it remains liquid. As we remove some of the gas from the top of the tank, the pressure drops a bit and some liquid turns to gas. The process continues until the tank is empty.

How is it stored?

Propane gas tanks come in various sizes, but all are high pressure containers. Small propane tanks could be disposible unitsthat hold a pound of fuel. These can connect directly to a torch or small propane grills.

Barbecue propane cylindersare very common and have a 20 pound capacity, which is 4.6 gallons of propane. In the United States and Canada (possibe other areas) they can only be filled to 80% capacity (16 pounds) for safety reasons.

I often see a pair of these on RV trailers. Having dual tanks is convenient so you have time to refill one tank while using the other.

That 20-pound size tank is used for gas grills, of course, but we use them to add capacity to our built-in tank in our motorhome. It's easier for us to swap out the BBQ tank at a gas station than try to find someplace that can fill our onboard tank.

After installing a tee adapter kit to my existing tank, I can use the onboard tank while we're driving. Then I switch to the BBQ tank when we set up on our campsite.

At our burn rate the BBQ tank typically lasts us at least a week of camping. The amount of fuel we use can vary quite a bit though. We only have to fill the onboard propane tank once a season.

Even larger tanks are used for home heat, I once had a home with a 500-gallon propane tank. The propane supplier would come to my home to refill since it's not reasonable for a homeowner to try to move a 500-gallon tank around.

How do I know if my propane tank is still okay?

Propane containers are stamped with various information. Different size tanks can have different markings due to different laws about how they are handled.

Some markings may start with the letters TW and some numbers, that's the tare weighting. WC stands for water content. What you're looking for are numbers only, no letters.

Tanks don't have an indefinite shelf life, they can rust and pose safety hazards.

Generally you'll see two numbers, a dash, then two numbers. It could be two numbers, a space, then two numbers. You might see the four numbers then the letter "E".

This stamp is in month-year format to express the manufacture or requalification date for the tank. There may be additional dates if the tank has been professionally re-certified to extend its usable life.

The good news is that tanks last a long time. A new tank is generally certified for 10 or 12 years from the date of manufacture. Each recertification adds 5 or more years, depending on the type of recertification performed.

The expiration date is generally at least 10 years after manufacture date, or 5 years after a retest date. Different countries have different laws.

More Than Just an Expiration Date

Whether you buy a new tank or a recertified tank, that long shelf life stamped on it is not a guarantee. Extreme weather and mishandling can degrade a tank faster.

Proper care means keeping your tank dry when possible. Check for visible rust – light rust is acceptable, deep flaking rust will compromise integrity.

Also be sure to check for signs of damage periodically to make sure it's still in good condition. It's quick and simple to do.

Failure points – connections and hoses

A lot of time you'll find that your tank is connected by a rubber hose. This is definitely something that will degrade after years of use. Direct sunlight and extreme heat can degrade rubber even faster.

Even with all metal tubing connected, the fittings can leak or damage can occur to tubing. Gas leaks are a major risk. Not only it is an explosion hazard, but it can be harmful to humans and pets.

If you can smell propane when no devices are running, you have an issue. Also check for cracks, kinks, and cuts.

A leak detector is a good, inexpensive way to help check.

Filling a spray bottle with a strong soapy water solution makes it easy to check fittings for leaks. If you see bubbles, you have a leak.

I like to check everything when I de-winterize since I'm already going through everything else.

Tank/Hoses/Connections are Good, Does the Propane Go Bad?

A common question is asking if propane goes bad over time; does it degrade? No, the shelf life of propane is considered infinite. Old propane will work just as well as a fresh filled tank.

Why Didn't I Just Say That From the Start?

The simple answer isn't fair! It would be easy to dismiss the rest of this article and assume you've received the answer you were looking for. It ignores complete safety measures for your stored propane tank and complete system.

It's very important to understand that propane fuel is only one component of your system. Make sure you don't have an expired tank, or worst yet damage or degradation to any part of your complete fuel system.

Final thoughts

Propane is one of the most ideal energy sources because it can be stored as a dense liquid for an indefinite length of time. With proper safety precautions the complete system can last for many years.

It's a good idea to periodically check the complete system of tanks, hoses, and fittings. Check the tank for expiry date as well as damage. Check everything else for leaks, cracks, and damage.