How to Interpret a Propane Tank Gauge

It’s Easy to Avoid Runouts When You Know What the Numbers Mean

While reading the gauge on your propane tank is easy—it’s a lot like the gas gauge on your car—knowing what the numbers mean can be confusing. After all, when we “fill up” your tank, the gauge will show your tank as 80% full. And you can’t wait until your tank is empty to call for a refill.

It’s confusing—we get it. Here’s everything you need to know to interpret propane tank gauge numbers, and why you never want to be 100% full or 100% empty.

Filled But Not Full

One of the most common questions we get is about why your propane tank gauge doesn’t read as 100% full right after we’ve made a delivery. The answer is in your high school chemistry book, and the reason is safety.

If you paid attention in chemistry, you know that liquids expand when they are heated. Propane, also called LPG or liquid propane gas, is transported and stored in a liquid form. What you may not know is that liquid propane expands a lot more, and a lot faster, than some other liquids. Propane will expand nearly 17 times more than water heated the same amount. That’s why, for your safety, an aboveground propane tank, which is exposed to the sun, is considered “full” at about 80%. That “space” provides a cushion against the pressure that builds up inside the tank. Underground tanks are typically filled to about 85% because they are insulated.

Keep in mind that the amount of gas in the tank doesn’t actually change when propane expands or contracts–only its density does. You might notice that the tank gauge reading fluctuates slightly during quick temperature swings (hot day, cool night), but don’t worry, that’s perfectly normal.

Under Pressure

Pressure is the same reason it’s important that you call for a refill before your tank hits empty, or even too close to empty.

All propane piping and fittings are coated with a pipe-joint compound to seal connections and prevent leaks. When you run out of fuel, it changes the pressure in the lines. When the pressure changes, it’s possible that the joint compound could contract and create a leak. While propane is completely safe under most conditions, it can be highly flammable, so leaking propane lines can be dangerous.

This is why it’s important that you call for a propane delivery when your tank hits about 20% full. That gives us time to schedule your delivery before your tank gets too low.

If you don’t call us in time, and your tank hits empty, we will need to conduct a pressure test to make sure everything is operating safely when we refill your tank after a runout. We also do this test when we install a new tank.

We Make It Easy

Of course, it’s good to know how to check the gauge on your propane tank, but it’s an easy task to forget about. That’s why we give you easier ways to make sure you get propane deliveries when you need them—without having to remember to check your tank and call us for delivery.

Admiral offers convenient automatic fill service as well as wireless tank monitoring. Either option makes it easier to keep your propane tank full without the hassle of runouts or the expense of pressure tests.

Contact us for more information about all we offer Tri-Cities homeowners today.