A common question propane dealers have when customers have a leak is "how much gas did I lose?". The answer is usually not that much. In reality, a small leak on a tank will result in the loss of a maybe a gallon of propane over a considerable period of time. However, all questions about leaks should be directed to your propane company. This page is only concerned with the amount of propane that may be lost as a result of a leak. Also see Checking For Propane Gas Leaks
Consumers often feel that a leak on their propane tank results in the loss of many gallons of propane gas. The following example will hopefully illustrate that the actual amount of gas lost is nowhere near what they envisioned. We've all seen a helium tank fill balloons and we're all familiar with the loud hissing noise and force at which the helium is coming out of the tank and into the balloon. If you hear a propane leak that's remotely similar to that of a helium tank filling a balloon, you need to be calling the fire department instead of reading this! We'll now use that which we're familiar with and attempt to equate it with propane.
Let's take a standard size balloon (like a party balloon), which holds a volume of roughly .5 cubic feet and for the sake of this example, you think your tank has leaked 10 gallons of propane. 10 gallons of propane equals 363.9 cubic feet of vapor which will fill about 728 standard size party balloons. Some customers believe the gas they have lost is over 50 gallons and if they have in fact lost 50 gallons of propane, that's enough propane to fill 3,639 standard size party balloons. Just one gallon of propane which produces 36.39 cubic feet of vapor will fill almost 73 standard size balloons or 2 standard size (18 cu. ft) refrigerators.
As you can see, the actual amount of propane lost in a leak is far less than most people realize due to the volume of propane vapor that is produced by one gallon of liquid propane.