By George Bliss
Propane tanks are pretty much maintenance free. Running with two 20-, 30- or 40-poundtanks and an automatic change-over valve, it takes only an occasional check to be sure you don’t run out of propane in your RV.
Every once in awhile you’ll want to know how much propane is left in a tank. You won’t want to run out and have your furnace quit on a chilly night or be halfway through barbecuing that roast with guests coming.
The most accurate way to measure your remaining propane is to weigh the tank. On the outside of the collar that protects the valve you’ll see various letters and numbers. Locate the letters “TW” stamped into the collar and note the numbers that follow. “TW” stands for Tare Weight which is the weight of your tank empty. Subtract the Tare Weight from the actual weight of your tank (bathroom scales work fine for this) and you’ll get the weight of the propane remaining in the tank. Generally, a 20-pound tank holds 20 pounds of propane, a 30-pound tank holds 30 pounds, and so on. If the Tare Weight of your 30-pound tank is 27 lbs, and your scale shows 40 pounds, then 40 minus 27 is 13 pounds. Thirteen pounds of propane in a 30-pound tank (13 divided by 30) equals 43 percent full by weight, so it’s almost half full.
There is an easier way if your tanks are mounted in a holder, as all RV tanks are, or if you don’t have a weigh scale handy. You don’t need to remove the tank(s), you don’t need to know the Tare Weight, and you don’t need to know propane weighs about 4.2 pounds per U.S. gallon. Take your kettle, fill with water and bring to a boil. Once boiling, pour the hot water in one place over the tank — where the tank collar meets the tank. After the kettle is empty, place your hand at the bottom of the tank where the hot water ran down the tank. If there’s any propane in the tank it will absorb the heat from the water and the tank will be cold. From that start point, run your hand upwards along the hot water path. When you reach the point where the steel of the tank gets hot, you’ve reached the level of the propane in the tank. You now know if you’re good to go or if you need to top-off or completely refill your propane tank.