Whether you’re using CO2 to keep the plants in your aquarium alive and healthy or for use in your paintball gun, it can be quite expensive to constantly replace spent CO2 tanks. Refilling these tanks can be a cost-saver, but not without first understanding refill the tank. If you are a novice, it’s better to let a professional refill your tank the first time around, as this is not an easy task for just anyone.
1. Be certain that the tank you intend to refill is completely empty. The best way to do this is to screw the CO2 tank into a disconnected air source adapter and let the tank bleed empty. If your CO2 tank is for a paintball gun, another method to empty the tank is to connect it to a paintball gun and repeatedly (and slowly) squeeze the trigger until you no longer feel a discharge of cold air from the barrel. Both methods are to make sure that the scales (see Step 3) are able to be zeroed properly later on, as well as for safety purposes.
2. Cool your empty CO2 tank by placing it in the freezer overnight. This helps condense the liquid CO2 in the tank.
3. Use a digital hanging scale to zero the CO2 tank. These scales can be purchased at most stores that deal in CO2 tanks and are often provided for use at public CO2 refill stations located at many sporting goods stores.
4. Connect your CO2 tank to the refill station. Ensure the connections are firm and sealed, to prevent any spillage.
5. Open both the cylinder valve (the one that looks like a wheel faucet) and your ball valve (the valve that looks like a handle) marked No. 1 completely to begin filling the CO2 tank. Fill the tank to between 80 percent and within a half-ounce of total capacity.
6. Close the cylinder valve and open the valve marked No. 2 to drain any liquid CO2 still in the hose.
7. Remove the CO2 tank from the refill station. Place the CO2 tank back on the hanging scale to make sure that the tank is not too heavy, which indicates that you have overfilled it. Should you overfill the tank, bleed some of the CO2 out using an air source adapter or by using the same connections to the refill station that you used to fill the tank.