Why Is My Propane Tank Only 80 Percent Full?


If you’re a keen observer, you have probably noticed that your propane tank only gets filled to about 80 percent of its actual capacity. The question is, why do we stop short of 100 percent full when we deliver your propane gas?

Like every decision made by our propane delivery team, this is done keeping your safety in mind.

You see, propane expands in the presence of heat, just like water does (propane is liquid when it’s stored under pressure at low temperatures inside your tank, but expands into a gas as temperatures rise). The only difference is that propane expands much more quickly than water when heated, and at a much greater volume. In fact, propane increases to nearly 17 times the volume of water over the same temperature increase! If your propane tank was full when exposed to a hotter environment (on a hot summer day, for example), it could become a dangerous situation.

That’s why our drivers only fill your propane tank to about 80 percent of its actual capacity. The extra space in the tank is a cushion against the pressure that builds up in a tank when it’s hot.

Our highly trained drivers use a pre-set gauge to make sure we don’t overfill your propane tank – one of the many measures we take to keep you safe at home.

To calculate the approximate fill capacity of your propane tank, multiply the tank’s total capacity by 0.8. Here’s a cheat sheet:

Tank size (gallons) 80 percent (gallons)
120 96
150 120
200 160
250 200
500 400

As you can see, when you become a Q-Dog customer, your safety comes first – now and always!

For safe, reliable propane delivery at the best prices around, trust the pros at Q-Dog – serving our neighbors in Calvert, Charles, St. Mary’s, Southern Anne Arundel, and Southern Prince George’s counties since 1945! Contact us to order your propane today.