How long can you keep propane in a tank?

Propane can be stored in tanks for extended periods of time if stored properly. The shelf life of propane depends on several factors such as the propane quality, tank composition, and exposure to elements. With proper care and maintenance, propane tanks can store the gas for many years.

Quick Answers

Here are some quick answers to common questions about propane shelf life:

  • Unopened propane tanks can last indefinitely if stored properly.
  • Opened propane tanks can last 12-18 months if cared for correctly.
  • Steel and composite propane tanks have longer shelf lives than aluminum ones.
  • Propane quality degrades over time, leading to potential performance issues.
  • Tanks should be stored upright, out of sunlight, and away from sources of heat or ignition.
  • Older tanks should be periodically inspected and tested for leaks.

How Propane Tanks Work

Propane tanks work by storing liquefied petroleum gas at high pressure. The interior of the tank contains porous materials that help absorb and contain the liquid propane. When the tank valve is opened, the change in pressure allows the liquid propane to vaporize into a gas that can then flow out of the tank. The porous materials inside the tank help ensure the liquid propane turns into vapor form consistently.

Most residential propane tanks hold between 24-120 gallons of propane when full. Large tanks are able to store hundreds of gallons. The high-pressure design allows a large amount of propane gas to be stored in liquid form in a reasonably sized tank. This allows the tanks to be portable and provide ample propane supply for use.

Types of Propane Tanks

There are a few common types of propane tanks used for residential and commercial purposes:

  • Steel tanks – The most common type. Durable and corrosion-resistant for long life.
  • Aluminum tanks – Lighter weight but less durable over time.
  • Composite tanks – Made from a tough, polymer material. Resistant to rust and dents.
  • Underground tanks – Installed below ground. Used for large propane supplies.
  • ASME tanks – Meet safety standards from the American Society of Mechanical Engineers (ASME). These include RV and motorhome tanks.

The construction and quality of the tank impacts its overall lifespan and ability to safely store gas long-term.

Shelf Life of Unopened Propane Tanks

Unopened propane tanks have an exceptionally long shelf life if stored properly. The propane inside is not subject to any environmental factors that can cause it to degrade while the tank remains factory sealed.

Here are some guidelines on the shelf life of unopened propane tanks:

  • Industry experts consider unopened tanks to have an indefinite shelf life if stored properly.
  • Tanks from a reputable supplier that have been stored properly can safely be used even after 10-20 years in storage.
  • The plastic seal on the tank valve indicates it has never been opened or used previously.
  • Steel and composite tanks have a longer shelf life than aluminum when left unopened.

As long as the sealed tank is stored upright and kept from rusting, the propane inside will not degrade and can last for decades.

Ensuring Quality of Unused Propane Tanks

While propane in an unopened tank won’t expire, there are some things to check before using an older tank:

  • Inspect the tank valve for any damage or corrosion.
  • Check the tank for dents, scrapes, or other external damage.
  • Confirm the plastic seal on the valve remains intact.
  • Check the pressure relief valve for blockages.
  • Do a leak test after connecting to equipment.

If everything checks out, even decade-old tanks that have been properly stored can be used safely. However, it’s smart to take some basic precautions given the age of the tank.

Shelf Life of Opened Propane Tanks

Once a propane tank has been opened and gas removed for use, the shelf life is reduced compared to a new unused tank. This is because the propane inside is now subject to potential contamination and degradation over time.

Here are some guidelines on opened propane tank shelf life:

  • Industry estimates range from 12-18 months for the shelf life of opened tanks.
  • The clock starts as soon as the tank is opened and gas released via the valve.
  • Propane quality can degrade faster in hot weather or tanks left in the sun.
  • Aluminum tanks have a shorter shelf life than steel when opened.
  • Tanks should be checked frequently for leaks once they’ve been opened.

Even if gas remains in the tank, old or dirty propane can cause issues with equipment after around 18 months. It’s recommended to refill used tanks at least annually.

Maintaining an Opened Propane Tank

To maximize the shelf life of an opened propane tank:

  • Only open the tank valve when actively using gas, keep it closed otherwise.
  • Store the tank upright and stable when not connected to equipment.
  • Keep the tank away from heat, sunlight, and ignition sources when disconnected.
  • Check the hose and fittings regularly for any leaks.
  • Consider adding a propane stabilizer additive if storing long-term.
  • Have older tanks recertified if they are more than 12 years old.

Careful storage and maintenance give opened tanks the best chance of retaining usable propane for a year or more.

Using Old Propane Tanks

Old propane tanks can often still be suitable for continued use if they have been properly maintained. However, there are some additional precautions to take when using vintage tanks:

  • Check manufacturing date stamped on collar or handles. Use caution if over 12 years old.
  • Inspect entire tank for damage, corrosion, dents, leaks, etc.
  • Confirm valve seal is intact on unused tanks before connecting.
  • Have an older tank recertified by a professional before refilling.
  • Perform leak tests on seal, hoses, and fittings when refueling.
  • Start appliance/equipment on low settings to check for issues.
  • Consider having vintage tanks professionally purged and cleaned.

Outdated or damaged valves, seals, and gaskets can cause propane leaks in older tanks. Handle them gently and take precautions when reusing after storage.

Recertifying Old Propane Tanks

Propane tanks that are more than 12 years old should be recertified by a licensed professional before refilling or continued use. This involves:

  • A thorough inspection for damage, corrosion, and leaks.
  • Replacement of seals, gaskets, valves if needed.
  • Pressurization and holding test.
  • Cleaning and purging of old propane if tank passes tests.
  • Application of updated certification label.

Going through recertification ensures vintage tanks meet modern safety standards before putting back into service. The recertification process typically costs $20-$60 per tank depending on size.

Signs of Bad Propane in Tanks

Propane naturally degrades over time, especially when stored in less than ideal conditions. Here are some signs that old propane tanks may have gone bad:

  • Discoloration, debris, or sediment in the gas.
  • Rotten egg smell, indicating rust, moisture, or sulfur contamination.
  • Equipment burns with yellow or orange flames instead of blue.
  • Appliances producing carbon deposits, soot, or backfiring.
  • Reduced efficiency and performance in equipment.
  • Tanks feel abnormally light, signaling leaks or gas loss.

Bad propane can damage equipment valves, burners, and lines over time. If old tanks exhibit any of these warning signs, it’s best to drain and refill with fresh propane.

Testing Old Propane Tanks

If an older propane tank’s quality is uncertain, there are ways to test it:

  • Visual inspection – Check for contaminants, corrosion, oxidation, etc.
  • Odor test – Propane has a strong, distinct smell if mercaptan has been added.
  • Combustion test – Burn a small sample to check flame color and performance.
  • Leak tests – Test tank seals, valves, and lines thoroughly for any propane leaks.
  • Pressure test – Tanks should maintain specified pressure levels.
  • Purge test – Drain a small sample into an approved container for inspection.

While opened tanks have a shorter shelf life, carefully testing and inspecting older tanks can extend their usable life in many cases.

Disposing of Old Propane Tanks

If an old propane tank cannot be recertified for continued use, it must be properly disposed of. Here are some guidelines for disposing of propane tanks:

  • Only attempt to dispose of empty tanks without any remaining gas.
  • Contact local municipal household hazardous waste program for disposal instructions.
  • Some retailers accept old tanks back for exchange or disposal.
  • Tanks can NOT be put in the regular trash once empty.
  • Let tank air dry outdoors for 1-2 weeks to fully evaporate any gas remnants.
  • Confirm tank is empty by running appliance/equipment until exhausted.
  • Do NOT attempt to cut, puncture, or dismantle old tanks yourself.

Check with your local waste authority to find approved disposal or recycling options for old propane tanks in your area.


With proper storage and handling, propane gas can be kept in tanks for extended periods of time. While unopened tanks have an indefinite shelf life, even opened tanks can retain propane quality for 12-18 months if maintained carefully. Check tanks thoroughly for damage, leaks, and other warning signs of deterioration before reusing after long-term storage. Have older tanks recertified and serviced by qualified professionals to maximize safety and lifespan. Follow local guidelines and regulations when disposing of old, expired propane tanks.

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