Methods of Refueling Propane Tanks

Last Revised: October 21, 2023

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Methods of Refueling Smaller Propane Tanks from Larger Ones:
Here I am simply presenting some information that I have found in other places. My own propane supplier won't allow me to make the connections needed to use any of the techniques below, but your experience may be different. I take no responsibility for the accuracy or use of the following information.

NOTE: Even if you don't plan to do any tank refueling yourself, take the time to read the information below about "Understanding the Markings on the Propane Cylinder"

With Bleed Valve and Pump
Most balloonists use this method of refueling. You go to the local propane dealer and utilize their pump the same way you would fill your vehicle with gasoline. The bleed valve on top of your propane tank is connected to a dip tube which extends into the tank. The end of the tube is at the 85% capacity level for the tank. When the liquid fuel reaches the end of the tube it spills out the bleed valve telling you that the tank has reached the recommended capacity.
1. Connect the hose from the fuel source to the main tank valve.
2. Turn on the pump.
3. Open the vapor bleed valve, the main tank valve and the fuel source valve. The tank will now begin to fill.

Although the sequence of these three events can be modified from this example it is important to establish a consistent procedure. The sequence of events is reversed for closing.
4. When the liquid propane begins to spurt from the bleed valve, close the fuel source, main tank valve, and the vapor bleed valve.
5. Turn off the pump.
6. If the fueling line has a bleed valve to discharge the fuel in the connector activate it at this time (newer pumps will automatically bleed when the pumping lever is released). If the system cannot be bleed slowly loosen the connection at the tank. The liquid propane in the line between the main tank valve and the fueling line valve will spurt out and vaporize. When the line is completely bleed you may disconnect the fuel line and/or fueling adapter.

Warning: Freeze burns are a hazard during this process so caution should be taken.

By Weight With Pump:
Like the prior example you would go to your local propane dealer (or they could come to you with a truck). This time instead of opening the bleed valve and waiting for the liquid to spurt out you fill the tank to a specific weight. As described below the procedure is somewhat more complicated. Since all balloon propane tanks have bleed valves why worry about this method? At least one state, Florida, in the late 80's considered a rule that would require all tanks to be filled by weight. Florida had experienced some problems (not balloon related) where the dip tube, which is screwed in, has come out and fallen to the bottom of the tank. Without this measure the tank will become completely filled before liquid propane comes out of the bleed valve. Read Overfilling Fires... beginning on page 18. Likewise should you suspect that this has happened you can check the accuracy of the bleed valve by using this method to refuel.
1. Connect the hose from the fuel source to the main tank valve.
2. Place the tank on a scale.
3. Turn on the pump.
4. Open the main tank valve and the fuel source valve. The tank is now filling.
5. When the tank reaches its full weight, close the fuel source valve and the main tank valve.
6. Turn off the pump.
7. Carefully disconnect the fueling line from the tank/adapter as described above.

Understanding the Markings on the Propane Cylinder

The full weight for any Department Of Transportation (DOT) certified tank can be calculated from information displayed on the tank. The water capacity and tare weight (empty tank weight) will be displayed on the tank. Water capacity is the weight of water the tank holds if it is filled to the brim with water. This is displayed on the tank immediately after the letters WC. Tare weight is shown on the tank immediately after the letters TW.

To calculate the weight of the tank filled, multiply the water capacity by the specific gravity of propane (about .5 at 70 F). Then multiply by .85, since the tank should only be filled to that capacity. This will give you the amount, in pounds, of propane that the tank can safely hold. Add to this the tare weight and you have the total weight when the tank is full (For "10 gallon" vertical aluminum tanks; Full weight = (103.6 x .5 x .85) + 26.5 = 70.5 lbs.).

Bleed Valve And No Pump:
This method is sometimes mistakenly called gravity feed. What is actually taking place is an equalization of pressure between two vessels. In this case our propane tank and the main fuel source. The method is used whenever a pump is not available such as a remote sight or transferring propane from one cylinder to another.
1. Connect the tank to be filled with the fuel source.
2. Open the bleed valve of the tank to be filled, the main tank valve and the fuel source valve.
3. As soon as liquid propane starts to spurt from the bleed valve, close the fuel source, the main tank valve and the bleed valve.
4. Disconnect the fueling line as described above.
This method can be accomplished using either the bleed valve or by weight. Filling a tank by this method will be slow. It works best if the receiving tank's internal pressure can be reduced well below that of the source.
Whenever you are refueling always wear gloves.