I often hear people asking about where they can get a large tank to fill their own C02 bottles. These larger tanks can either be purchased or rented from such places as carbonics supplies and welding shops/supplies as well as other similar local area commercial businesses. You can put a deposit on the tank and rent it or just purchase the tank depending on your available funds and how often you need fills. You can sell fills to your friends and make a portion or all of your investment back as well. The tanks range in size up to 50lbs. For paintball I would not suggest anything under a 15lb - 20lb tank as it's not worth your time to use anything with less a capacity than that. I pay about $12 to have my 20lb tank filled and it works out to be about 4 cents an ounce for fills. It's very convenient having your own fill tank, especially if you like to tinker often. Running out of propellant right in the middle of an experiment or adding a modification is a bit frustrating when you want to see the results or use your chronograph. You will need a fill adapter for your large fill tank and they can get a little expensive. I will show you how to make your own and give you some advise on filling those bottles as well.
Parts, Materials and Tools
The materials you will need can most likely be purchased from a local welding supply, carbonics supply or similar. I can't tell you for sure what your local supply shops will have in stock so it's best to look in the yellow pages and call around before just visiting one and finding out that they don't stock these particular parts. If when you call you find that they don't have them, ask if they know of another local business that might.
You will need (2) CGA 320 nipples and washers, (2) CGA 320 hex nuts, (1) 1/4 inch threaded full port on/off ball valve and some teflon tape. The nipples come in different lengths so try to get one that's about 2.25" - 2.5" long so the lever of the ball valve will clear the hex nut when turned wide open. The tools you will need are an 11/16" and 5/8" open end wrench. To turn the final assembly onto the valve of the tank you'll need a 1.25" open end wrench. You may use adjustable wrenches as well but you'll need more than one to complete this task. You'll need a spool of teflon tape to seal the threads of the nipple shaft end to the threads of the on/off ball valve. You might use the yellow tape used for gas connections because it's much thicker and less cumbersome than the thinner white type.
Assembling The Components
Put the hex nuts on the nipple shafts facing outward as shown in the photograph above. Apply a couple layers of teflon tape tightly to the threads of the nipple shaft ends. The tape should pressed into the grooves of the threads. Be sure not to apply the tape past the end of the threads so the tape won't fray and enter the bottle valve when you're filling it. Start turning the threads of the nipple shafts into the threads of the ball valve to get them started. Once hand tightened use the wrenches on the hex areas of the ball valve and end of the nipple to tighten them as best you can. Voila, you're done!
You will need the (2) washers that came with the nipples to seal the assembly to the fill tank valve and bottle valve. You can either leave them loose or epoxy them to the hex ends of the nipples. Just be sure not to epoxy the hex nut in place too because it needs to move freely when attaching the assembly to the fill tank valve and bottle valve.
Filling A Bottle With Your Home Made Fill Adapter
You must take caution filling your own bottles because if performed in the incorrect manner, can be potentially dangerous or even cause death. Always weigh the tank before and after your fill to be sure that it's not overfilled. This is especially important after getting your large fill tank freshly filled. It is imperative to have an accurate scale when filling your own bottles. You can get a relatively inexpensive digital fishing scale at your local sporting goods store or department store. IF YOU ARE CONFUSED BY ANY OF THE FOLLOWING, DON'T ATTEMPT FILLING YOUR OWN BOTTLES AND HAVE A PROFESSIONAL FILL IT FOR YOU.
You'll need a siphon tube installed in your large fill tank. This is simply a tube inserted in the bottom of the pressure valve in the tank that goes to the bottom of the tank. The tube will transfer liquid C02 directly from the tank into the bottle. If you do not install a siphon, all you will transfer is a small portion of pressure to the bottle.
Before even attempting to fill your bottle, you must know the exact weight of the bottle when it's empty. Always use ounces when calculating the weights to avoid any confusion and after convert to pounds.
Here's an example using a 16 oz. bottle:
- 16 oz. Bottle = 1 lb 12 oz. empty weight
- 1 lb 12 oz. = 28 oz.
- 28 oz. + 16 oz. fill = 44 oz.
- 44 oz. divided by 16 oz.(1 lb.) = 2.75 lbs.
- 2.75 lbs. = 2 lbs 12 oz.
You'll need to chill the bottle before filling it. The colder the bottle, the less pressure or resistance is exerted from it hence the easier it will accept pressure. If you do not chill the bottle before filling, you will end up continually failing to completely fill the bottle. You may notice that when getting a fill at your local pro shop or field, they will fill the bottle then purge it to cool or frost the bottle then give it a final fill. Since you will be at home there's a more simple manner to accomplish this and it will save on wasted C02 at the same time. By putting the bottle in the freezer of your refrigerator for about 20 - 30 minutes before filling it, you have essentially done the same thing and you won't need to purge or waste any leftover C02 from your last fill at the same time. There can be a potential danger in doing it this way though. You can easily over fill the bottle so you'll always need to weigh your tank after filling it. If it is overfilled, after the chill is gone the pressure will rise past the burst point of the burst disk in the bottle and rupture it spewing C02 from the bottle.
When using this home made fill adapter, you cannot weigh the bottle while filling it as you can with the more expensive fill adapters. You'll pretty much have to play it by ear. Most times when filling a bottle, the pressure will equalize and not fill past the capacity of the bottle. The exception to this is if the fill tank has been freshly filled. After a few fills taken out of it this is not an issue though.
To fill the bottle just install the fill adapter to the fill tank and be sure to put the washer that came with the nipple between the tank valve and adapter. Do the same when attaching the bottle to the other end of the adapter. If you don't use the washer(s) there won't be a complete seal and it will leak. Turn the ball valve on the adapter to the off position. Now you can turn the pressure on from the tank. Turn the ball valve arm to the on position and you will hear the pressure releasing into the bottle. Once you hear the pressure subside or cease, turn the ball valve arm to the off position once again. Use the wrench and remove the bottle from the adapter. Weigh it and be sure you didn't overfill it from the calculations of weight you made earlier. If it's overfilled you can purge the bottle a little at a time until you've reached the correct weight. Purging the tank can be done by pounding a flat head nail into a piece of wood like a table, work bench, 2 X 4 in your garage, ect. Put the valve pin on the bottle on the nail head and press the tank and valve on it forcing the pin down to open the valve. Do this shortly then check the weight again. Keep doing this until the weight is correct. Do not just use a screwdriver or similar to purge the bottle because you can freeze your hands. The temperature of C02 coming from the bottle can be some -50*. After you've filled your tanks a couple of times it actually becomes routine and you'll pretty much know when to turn the valve off and be less likely to overfill or underfill the bottle.
Now you've saved some cash by making your own fill adapter and saved even more by purchasing or renting a large fill tank. My tank was made from an old fire extinguisher and have had it for quite a while. I just replaced the initial hose and valve with a valve with an on/off knob. It may cost a little cash in the beginning but will pay off in the long run not to mention the convenience of not having to depend on a pro shop or field to fill your tanks all of the time. Purchasing bulk C02 is a great savings as well.
Technical Information
