We have a 100-lb propane gas tank that we use for our gas stove.

We never know if the tank's almost empty, and I always wonder if we're changing it too soon.

Is there an accessory that I can add to the line that will let me know how much gas is left?


  • 1
    Pour a kettle of boiling water down the side of the tank. Then touch the bottom, and slowly move your hand up until it gets hot. There will be a very clear line between hot and cool where the liquid level is.
    – Mark
    Commented Jan 8, 2018 at 1:47
  • 1
    yes, a device known as a scale will tell you how much is in an other-wise empty tank ;)
    – dandavis
    Commented Jan 8, 2018 at 5:58

4 Answers 4


Keep a spare tank and always bleed them dry.


In my last house, we had propane for cooking. We had the same problem as you until we contacted a propane dealer who would come on a regular schedule and refill our tank and only charge for the amount we needed. It cost a little more but is was well worth the added cost since I no longer had to take the tank somewhere to be refilled. At a later date we added a second tank with an automatic switch-over with an indicator of the status of the empty tank. The propane dealer could then come and fill the empty tank. This way we always had a spare tank in case of a near disaster such being isolated due to a snow storm or a flood and we could use the kitchen stove for heat in case the furnace quit.

  • Our local dealers have a US$200 minimum charge, which is almost 2/3rds of a tank at last prices. I hadn't thought about using one tank at a time to have a means of managing using the same method you suggest. Great idea. The tech told me for the generator, we need the higher flow of both tanks combined, though.
    – fred_dot_u
    Commented Jan 8, 2018 at 22:40

Yes there is, but it's not added to the feed line. It's an astonishingly simple device. It's a liquid crystal thermometer mounted on a magnetic strip. You apply the strip (after it's been flattened out from the packaging) to the tank in a vertical orientation.

Pour boiling hot water (is that redundant?) over the tank area around the strip. This causes the propane in the tank to vaporize in that area, cooling the liquid down and warming the gas. The thermal capacities of the strip change color and the line between the two colors shows the level.

tank level indicator

I've used it a few times, although my color-blindness required another set of eyes to determine the correct level.

Since then, I've purchased a Flir-One which also presents temperature differences by color change. No need for the strip, just the hot water on the tank and the level is clearly indicated on the screen.

The magnetic strip is orders of magnitude less expensive than a Flir-One, but far less entertaining.

Flir-one tank level

The image above shows my tanks. The left one having been doused with hot water, the right one in progress.

  • You can also do that by firing up a burner. When you use propane gas, it boils out of the propane liquid, chilling the liquid. We recognize fill level on tanks by the line of frost. Commented Jan 8, 2018 at 21:59

Not one you add to the line, but if your tank is even vaguely portable you can put it on a scale to weigh it. Special propane scales exist.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.