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The 80/20 Tank Fill Rule: What’s That?

A quick lesson on the science of propane

80 20 rule maineHave you ever checked your propane tank gauge after PitStop Fuels has made a propane delivery to your home and thought that we made a mistake because your tank is only 80% full? Trust us. It’s no mistake! It’s actually intentional. And there’s a good reason behind that: your safety. We’ll explain:

Propane tank science

Propane (chemical formula C3H8) is a liquid. Like other liquids, propane expands when it is heated. Propane in liquid form cannot be burned. To ignite so it can be used in your home’s heating system, water heater, range, or whatever appliance you are using it in, propane has to be able to e x p a n d.

But, propane expands a great deal more expansion room than other liquids. For example, propane expands at 17 times the expansion rate of water in the same conditions. You can read more about propane volume here if you’re interested.

When you get a propane delivery, we, or any other delivery company, must leave empty space in your propane tank to allow for that kind of expansion. Let’s say you have a 500-gallon propane tank: We fill it to 400 gallons. That empty space remaining is the room given so the propane can safely expand.

Also, propane expands in the presence of heat. If there’s no room in the tank to allow for that expansion, it could create a very dangerous situation!

Why do my propane tank gauge levels fluctuate?

Sometimes, you may see fluctuation in your propane tank gauge levels; especially when there are fast temperature swings from a hot day to a cool night. Don’t worry, this too is a normal occurrence. This happens because the density of the propane in your tank is adjusting as the temperature changes. The amount of propane in your tank hasn’t changed, it’s just either taking up more room as it expands or it takes up less room as it contracts back to its normal size.

Light is right for propane tanks

Have you ever thought about painting your propane tank a darker shade to match your house or blend into your landscaping? DON’T DO IT. Propane tanks are light for a reason. Lighter shades like white or beige reflect the outside heat. Darker colors absorb the heat, which creates dangerous levels of propane gas expansion.

PitStop Fuels is committed to the qualities that have kept us in business for more than 30 years – and your safety is always priority number one! For safe, reliable propane delivery year-round, you can count on us. Become a customer and experience the difference today. We’d love to have you with us!