How Propane Tanks Work

Delta Liquid Energy propane tank

Let’s have some fun and learn about what all those valves on your propane tank are for. These tanks have been engineered with your safety as the number one priority. Combined with efficient construction, it’s amazing how these tanks work. While these tanks are designed to be safe, please keep in mind that propane can be dangerous if handled incorrectly. All adjustments to the tank, including the removal of valve caps, should only be done by trained professionals. Let’s learn how propane tanks work!

Tank at a Glance


Breakdown for the parts of the propane tank

1. Liquid Evacuation Valve and Tube:

This is either located on the top of the tank, or underneath in older models. A hose is connected to the valve when propane needs to be removed from the tank. If the model has a valve on the top of the tank, this is removed through a tube sticking down into the tank to collect the propane. This is especially useful when the tank needs to be moved, as it must have less than 5% fill remaining inside.

2. Fixed Liquid Level Gauge:

This is used to determine the level of the tank while refilling. Most level gauges are set to approximately 86%, although some manufacturers set it to 80%. Since propane expands as it gets hotter, filling a tank above 86% capacity can create too much pressure inside. This is especially dangerous if the temperature around the tank increases, which will cause the pressure inside the tank to expand. The valve for the fixed maximum liquid level gauge is underneath the tank dome. Attached to the gauge valve is a dip tube that extends down to the 86% full fill line. When your delivery specialist is filling the tank, they will watch the fixed liquid level gauge. When the tank is at 86% capacity, the dip tube expels a small amount of propane through the level valve and the specialist knows the tank is at capacity.

3. Float Gauge:

Are you wondering how to tell how much propane is in your tank? It can be found on the dial gauge, which is underneath the tank dome. Attached to this dial is the float gauge, which extends down inside the tank to the propane liquid level.

4. Pressure Relief Valve:

The pressure relief valve will automatically vent propane vapor if the tank becomes over-pressured. The relief valve is held closed by a powerful spring that opens when the pressure inside the tank increases.

5. Tank Dome:

Features such as the dial gauge are found underneath. These, plus the valves located outside the dome, are described in more detail below.

Valve and Gauge Details

Tank Icon Gauges

1. Fill Valve:

By opening this and attaching the propane hose from the bobtail, delivery specialists refill your tank. It’s easy to spot since it’s usually one of the largest valves on your tank.

2. Liquid Level Float Gauge:

This indicates the fuel level within your tank. By reading the percentage on the gauge, you can tell roughly how much propane you have left and when it will be time to call for a delivery. Per our requirements, you must call when your tank is at 30% full. This ensures our team has enough time to add you to a regular delivery route and helps prevent your tank from running out of propane. In cases where the tank is less than 30% and needs an emergency delivery, off-route and reconnect fees may apply.

3. Withdraw Valve:

This is sometimes located underneath the dome, but otherwise it will be found towards the end of one side. Wherever it is located, do not use this to attempt to withdraw propane yourself. This is only for professionals to use in the event that your propane needs to be removed from the tank.

4. Fixed Liquid Level Gauge:

A delivery specialist will periodically open the fixed liquid level valve while refilling your tank to ensure it does not become overfilled. As before, this will alert the specialist when the tank has reached 80% or 86% full, depending on the tank manufacturer’s settings. Since opening this valve releases vapor, it should only be done while using the correct protective gear. To avoid burns, the skin must always be protected when there’s a potential exposure to propane vapor. Since the liquid level gauge can have errors in reading the amount of propane in the tank, this is a more secure way to ensure that it isn’t overfilled.

5. Vapor Equalizing Valve – NOTE: This is not used in California:

For our North Las Vegas residents, we’re keeping this information in. For those in California, this valve will often be present on your tank but never utilized by your delivery specialist due to state regulations. The vaper equalizing valve is a bit like the relief valve since it is there to prevent the tank from over-pressurizing. However, this is intended to relieve pressure during the filling stage instead of at rest. While a delivery specialist is filling your tank, a hose is connected to the equalizing valve, and excess pressure can be vented back to the bobtail truck.

6. Relief Valve:

As mentioned in the previous section, this will vent propane vapor if the tank becomes over-pressured. Never look directly into the relief valve when the cap is removed. It is engineered to operate at or above 250 PSI. This valve should only be handled by professionals. Like most the rest of your tank, it’s engineered for your safety but can still be dangerous if used incorrectly.

7. Service Valve:

 In the event that you need to shut off the tank, this valve can be used to do so. To turn it off, turn clockwise (to the right). This controls the vapor service and, by shutting it off, will shut off all propane gas flowing from the tank. If you think you have a leak and shut off the tank, it is required that a professional inspect it before turning it back on. Never turn your propane supply back on yourself once it is off. This always needs to be done by one of our certified technicians. This is connected to the propane regulator.

8. Regulator:

 Propane regulators are sometimes considered the heart of your tank since they keep the propane flowing. Since the propane inside the tank is so highly pressurized, the gas heading to your appliances needs to have the pressure lowered. The regulator accomplishes this and helps keep you and your appliances safe. The pipe connecting the service valve to the regulator is referred to as the “pigtail”. In snowy climates, the regulator is located under the tank dome.

Wait! Some of my valves looks different:

Combination valve for a propane tank

In some older tanks, you might see or even have these combination valves. In this case, the Vapor Equalizing Valve (again, not used in California), the Fixed Liquid Level Gauge, and the Service Valve, are combined into one system. They still fulfill their individual purposes like this. However, this model is becoming less common as more and more tanks are being made with the valves and gauges separated.

And those are the basics of your propane tank! Please do not open the valves or attempt to dismantle your propane container. As your trusted propane provider, we at Delta Liquid Energy are here to answer any questions you have regarding your tank.