What’s The 80/20 Propane Tank Fill Rule?

Written on: January 11, 2021

Putting Your Safety First—With Each And Every Fill-up!

about 80 20 rule texasHave you ever come home after a propane delivery, checked your tank, and seen that it’s only 80% full? You may initially think to yourself “they didn’t even fill it up all the way! What gives?!” We assure you—this is not a mistake or an accident.

This is purposefully done not only by Pico Propane’s dependable delivery drivers—but by all propane companies and their respective teams as well. It is for your safety—and the safety of your home.
To understand it, you need to understand the science of propane.

The Science Behind This Safety Standard

The propane (chemical formula C3H8) in your tank is stored as a liquid. The liquid changes to gas before it leaves the tank. Hence why it’s technically called liquid petroleum gas (LPG).

Like any liquid, propane will expand when its temperature rises. The difference with propane is that it expands a lot—and quickly too! Propane’s volume increases nearly 17 times the volume of water over the same temperature increase.

That expansion is why your delivery driver needs to leave extra space in your tank. Your propane needs room to safely expand. Aboveground propane tanks are typically filled to about 80% capacity. Underground tanks can be filled slightly higher because they are insulated against the heat.

That extra space in the tank provides a cushion against the pressure that builds up inside the tank. For example, a 500-gallon tank filled to 80% will safely hold 400 gallons of propane.

This safety practice is especially important in hot weather. That is when liquid propane will expand the most. The amount of gas in your propane tank does not change during periods of expansion and contraction, only its density changes.

If you notice that the tank gauge reading fluctuates slightly during quick temperature swings like hot days with cool nights, that’s actually perfectly normal!

Propane gas expansion is why you should also NEVER paint your outdoor propane tank a dark color. Dark colors absorb more heat and could cause the propane in your tank to expand to dangerous levels.

Safe Propane Deliveries You Can Count On!

No matter what your tank gauge currently reads—you have to have a propane delivery company that you know will be there for you when you need them most. And guess what? Pico Propane & Fuels is that company!

With Pico’s Keep-Full automatic propane delivery, we’ll use your propane usage history and current weather to schedule a delivery to your home before you run low. If you want even more peace of mind, we also offer wireless propane tank monitoring so you can see with our app any time of day or night just how much propane is in your tank. We also see this information, so we can be even more accurate in scheduling your propane deliveries.

From Central New Mexico through South Texas and into the Gulf Coast, Pico Propane & Fuels gives customers the safe, reliable propane delivery they depend on. Become a customer today and experience the difference we can make for your home or business!