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Propane Tanks & the 80% Fill Rule

How many gallons of propane are in a 120-gallon tank? Some of you may recognize this as a trick question. The tank has a 96-gallon capacity. So why aren’t propane tanks ever filled up all the way? That has to do with the 80% fill rule.

The 80% fill rule is a preventative safety measure against the fluctuations that happen inside a tank. Propane, like water, will expand when heat is added to it. Propane, however, will increase in volume nearly 17 times greater than water over the same temperature increase. To allow for this expansion, propane containers are filled to only 80% of their capacity.

That means a tank that is 80% full on a mild March day, might register as 85-percent (or higher) at the mid-July cook out. It’s the same amount of propane, but it’s taking up more space. So the extra space in the tank is a cushion against the pressure that builds up in a tank when it’s hot.

Want to know the fill capacity of your propane tank? Multiply the tank’s total capacity by 0.8. Here’s a handy cheat sheet showing you total number of gallons remaining based on your tank size and current gauge level.

80% tank level

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  1. Posted February 28, 2015 at 12:44 pm | Permalink

    We are out of propane after ordering over 10 days ago.Amerigas service is pathetic and we will cancel our business on Monday 3-2-15.Failure to deliver.

  2. Norma Connell
    Posted April 9, 2015 at 6:25 pm | Permalink

    Have been a customer of Amerigas (previously National Butane) for 43 years. Their customer service has progressively declined to the point that I am now shopping for a new gas provider. In 1972, they furnished a 250 gal tank for no charge in order to secure business. Without warning, a few short years ago, they started charging $70 /year. I explained I was a senior citizen on a fixed SS income, to no avail. I have always used their budget pay and then last year, my budget pay was set at $213/mo. I only use propane for heat. I called several times complaining because previously my payment was less that $100. Now, April is my settlement month and I was notified my payment for this year will be $74. This is in addition to a $1200 credit to my acct from last years’ ridiculous monthly charge. They refused to refund my excess paid in without removing me from the “budget Pay”. Next year they will have one less senior citizen to take advantage of. Steer clear of these abusers . They don’t deserve your business.

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