How much LP is left in that cylinder?

If you've ever been caught with empty propane cylinders, you know how annoying it is. But how can you really tell how much LP is left in your cylinder? Motorhomers often have a gauge on the side of their LP tank that tells them where they stand, but not so for the travel trailer set. There are various methods and devices that can help you. Here's a quick look.

For folks with dual LP cylinders, most automatic changeover regulators will show you a "flagged" condition. Typically a green "flag" indicates there's still LP in the cylinder that the pointer indicates. If the cylinder is empty, the green flag goes red. But that still doesn't tell you how much LP is left in a "good" cylinder.

Some RVers invest good money on "in-line" gauges that install between the cylinder valves and the RV's gas inlet pigtails. They definitely tell you when you've run out, but the trouble is, since they're pressure activated, it's not until there's barely any gas left in a cylinder that you get a warning that you're running short. Many RVers who've invested close to $20 a pop for these gauges say they're sorry they ever did.

Then there are "tape on the side" indicators that use a temperature differential method to indicate how much fuel is left in the container. In theory the thing is simple and easy to use. You stick a magnetically mounted "tape" on the side of your cylinder (two for 7 gallon cylinders), pour hot water over the tape, and in a few seconds a color difference will who where the level of LP is in the cylinder. Trouble is, many users report that they can't get the thing to stick to the side of their tanks, as the product is delivered folded up, and once straightened out, doesn't work well. At about $5 each, maybe you'd want to "chance it."

One sure fire way (if you'll pardon the expression in connection with propane) to check your level is by weight. It's a bit of a hassle, but after disconnecting your LP cylinder from the RV pigtail, simply weight the cylinder with a digital scale (like those sold for weighing fish or luggage). Subtract the tare weight of the cylinder (imprinted on the collar of the tank, preceded by the letters TW), then divide the result by 4.11 (weight of LP per gallon) and you'll know how many gallons of LP remain.

A recent entry into the 'how much is left' arena is an ultrasonic testing device called the Truma Level Check. An electronic gadget, it's held against the side of the cylinder, a button pushed, and the user looks for an LED. If the LED is red, there's no fuel at that point in the cylinder. Move the device downward on the cylinder and try again repeatedly until you get a green light. We've never tried one of these, so we can't vouch for it. At $65, if it works, it could make you the envy of the campground.