How to Tell If a Propane Tank Is Empty

Many of us only think about a propane tank when it's time to "fire up the barbie." Others may use propane in leisure activities, such as camping in RVs or going out in a boat. Wherever it is that you use a propane tank, there is one pressing issue when you go to use it: Does it still have propane left or is it time for a propane refill? There are simple ways to address this issue that give you an idea of when you are running on empty, and there are more complex methods to test the contents of your tank when precision is required.

Grilling marinated turkey breast on a gas babrbecue
credit: Victor Cardoner/Moment/GettyImages
How to Tell If a Propane Tank Is Empty

Propane Tank Gauge

Nothing is more disappointing to you and your family than getting food ready to throw on the barbie, then finding out your propane tank has no propane. Empty propane tanks can present even more serious consequences in an RV or boat.

The first and easiest way to tell how much propane remains in a tank is to look at the propane tank gauge. This is a gizmo connected to a propane tank level sensor. Like a fuel tank gauge on the car, the propane tank gauge lets you know whether you have a quarter tank, a half tank or more.

Easy Propane Test

If your tank doesn't have a propane gauge, here's a simple way to get an idea of how much is left. Keep in mind that your tank stores liquid propane in the base, but toward the top is vapor, sitting on top of the liquid.

Get a cup of very hot water and dump it down one side of the outside of the propane tank. The tank is made of steel. While the part in contact with the vapor turns warm from the water, the part in contact with the liquid propane won't. So just feel along the propane container top to bottom to determine where the steel starts being cold. That tells you the level of the liquid propane in the tank.

Of course, this provides an estimate, nothing more. It can help you figure out whether to get a propane refill. For more precise measurements or when accuracy is mandated, you'll have to weigh the tank.

Weighing a Propane Tank

If you really need to know how much propane is left in your tank, the only accurate method of measuring this is by weighing the tank. You compare the weight of the empty container to the weight of the full container. The difference represents the amount of propane remaining, and lets you know whether you are ready for a propane refill.

Fortunately, weights are marked on every propane tank. Look carefully and you'll find two different weights stamped on the top handle of the tank. The first is the tank's weight when empty, called the "tare" weight. The other number is the weight of the tank when full. The most common tank for use on grills and other small outdoor propane appliances is a 20-pound tank, which weighs 38 to 40 pounds when full and 18 to 20 pounds when empty. Note that regulations mandate that propane containers can only be filled to 80 percent capacity. That means that your tank should be considered full at 20 pounds.

If your tank currently weighs 28 pounds and the tare weight is stamped in at 18 pounds, the difference is 10 pounds. Since 20 pounds is the maximum, it can safely hold, at 10 pounds, it's currently half full.