Understanding the 80% Fill Rule for Propane Tanks

image of a propane tank gauge and propane tank levels

If you’ve ever taken a peek at the gauge of your propane tank after a propane delivery and you see that your propane tank levels are hovering at around 80%, you may question why. We understand that a full tank means long uninterrupted heating and will help maximize every propane delivery. But why do we do this?

It’s actually because it’s a means of precaution.

We didn’t make any errors here because we really intended not to fill your propane tank up to the full level. This is an industry standard that all propane delivery companies follow – the 80% fill rule.

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Understanding Your Propane Tank Levels

In this article, we’ll discuss several reasons why the 80% propane tank rule exists in the first place.

Leaving Room For Propane Expansion

image of propane tank

Heat causes things to expand. However, the rate of this thermal expansion differs between substances, so it’s really impossible to predict how much it will expand.

For example, propane expands 17 times more than water over the same temperature increase. And though this difference may not be a problem when you’re in an open space, things are a lot different when we talk about enclosed spaces.

Because propane tanks have fixed dimensions, the next best thing propane delivery companies can do is plan this expansion. We need to leave some room, at least 20%, so propane can expand as much as it needs to, reducing the stress on the tank.

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The Effects Of Propane Tank Location

Where you put your tank can affect its temperature.

If you install your propane tank underground, there’s better insulation against the sun’s heat, so interior temperatures tend to remain stable. Because of this, we might probably be able to go over the 80% limit, and you won’t have to worry about the reduced buffer as the tank is under favorable environmental conditions.

However, if you place your propane tank above ground as most propane-fueled homes do, it’s probably best to ensure that it’s shielded from sunlight and other heat sources.

If you want to go over that 80% rule, you can even call a fuel delivery company near your area and consult about additional insulation if possible.

It’s All About Propane Safety

image of paper cut out of family in hands depicting propane safety

Providing a 20% free space ensures your safety. If we didn’t do this, any amount of heat expansion can result in immense pressure against the tank walls.

Although a propane tank material can hold minor temperature increases, large temperature swings can be very dangerous. When this happens, weak points in your tank will burst open, and leakage would occur.

When it comes to these things, we tend to always err on the side of caution.

All propane delivery services are aware of the tendency for propane gas to increase in volume drastically. You can’t expect any delivery services to fill your tank over 80%, and the 20% free space is enough to ensure your safety.

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The Effects Of Propane Tank Color

You’ve probably noticed that propane tanks tend to be painted with white or a lighter shade. There is a good reason for this. If we go back to physics, the white color or lighter colored surfaces reflect light while black surfaces absorb light.

This very same principle is demonstrated in residential roofing, wherein light-colored roofs tend to keep homes a lot cooler than dark-colored ones.

For this reason, propane tanks are painted lighter hues. And because propane gas is very sensitive to heat, it makes it very important that the container is of a lighter shade.

So, even if you think it doesn’t match your home’s aesthetics, never repaint your tank with a darker color.


The Normalcy Of Propane Gauge Fluctuations

Propane gauge readings always tend to fluctuate throughout the day, even if you don’t use propane. It always happens, and there’s nothing to worry about.

Fluctuations don’t mean that your gauge is broken or the amount of fuel lessened. These small fluctuations are usually caused by changes in temperature throughout the day.

You can actually check this out yourself.

Check your gauge around noontime, and you’ll likely get higher readings compared to when you check it again at midnight. This is because, at noon, the sun is higher, which allows the propane to expand inside and will shrink back once the temperature is cooler. So, basically, the propane gauge can detect this movement.

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The Insignificance Of Propane Tank Size

The truth is, the propane tank size is really insignificant. Every propane delivery company knows the buffer rule, so there’s a standard as to how much you should put in a tank. Here are two examples:

  • A 200-gallon tank can only hold up to 160 gallons of propane, wherein 40 gallons serve as the expansion buffer.
  • A 500-gallon tank can only hold 400 gallons of propane, wherein 100 gallons is meant for the expansion.

Many people assume that if you have a bigger tank, a smaller buffer percentage should just be enough. For example, if you have a 500-gallon tank, you can fill it up to 90%, and a 50 gallons buffer should be enough.

But, this is wrong.

The truth is, the larger the tank size, the greater the expansion once it heats up. That’s why it’s very important to maintain that 80% fill rule no matter what the tank size is.



Propane delivery is not as simple as calling for delivery and refilling your tank. No. It’s a very well-thought-out process.

Propane delivery trucks come to your home with enough fuel for all customers who ordered, and each household should receive the exact amount they need. Service providers will then check the tank size, calculate the required buffer, and fill your tank to a safe level – the 80% fill rule.

Now, when this is going on, you don’t have to worry about any heat-related dangers. But if you do have more questions about how this whole process is done, feel free to call your propane provider or Townsend Energy.

<h2″>Call Townsend Energy For All Of Your Propane Needs

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Townsend Energy offers superior propane deliveries throughout New England. Our propane delivery services are always fast and reliable. We offer various propane delivery plans and propane financing options. This way, you can customize your propane deliveries to meet your needs. By ordering your fuel from us, you can expect to pay the best propane prices in all of New England.

Also, Townsend Energy offers a full line of HVAC services. Therefore, by working with us, you can use the same service provider for your propane deliveries as you do for your furnace repairs, heater maintenance, and heating system replacements. Townsend Energy is a family-owned and operated company that prioritizes its customer’s needs and satisfaction. We also back our work with a written guarantee. Call today to find out what Townsend Energy can do for you!

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