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Why Isn’t My Propane Tank 100 Percent Full?

Posted: February 10, 2017

80% graph

Ever wonder why we stop short of 100 percent full when we deliver a gas to your propane tank?

Like most things our propane delivery teams do, it’s for safety reasons.

Propane expands in the presence of heat – just like water, except much more quickly 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 tank is full and the temperature inside the tank rises (if your tank is in the outdoor heat, for example), it becomes a dangerous situation.

That’s why our drivers only fill your outdoor above-ground propane tank to about 80 percent of its actual capacity (we can add a bit more to in-ground tanks because the ground insulates them from big temperature swings). 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