The purpose of this thread is to answer all the commonly asked questions about filling compressed air tanks. This thread is split into several posts, broken down by category. This first post will explain the basics of air fills, and the options available. The posts following this one are FAQ's, specific to each type of system. The FAQ's break down as follows:
Types of Fill Systems (in order of set-up cost, lowest to highest)
Scuba Tank ($200 - $500)
Bulk Tank/Cascade ($500 - $2000)
Booster ($2000 - $4000)
Frequently Asked Questions--General
Can I fill my paintball tank with my shop compressor?
No. Most shop compressors run at 125-150 psi.
Can I use a booster with my shop compressor to fill tanks?
No. Boosters require two pressures of air to operate--drive air and supply air. While you can use your shop compressor for the drive air, you still need a higher pressure of supply air. To operate efficiently, you'll need to provide a supply air pressure of 1000 PSI or higher.
How do I determine what type of fill adapter I'll need for my supply tank(s)?
Stamped on the valve of the supply tank is a CGA number. This number is what you'll need to purchase the correct adapter. 2200 PSI bulk tanks commonly use a CGA 580 or CGA 680 adapter.
Frequently Asked Questions--Scuba
Where can I buy a scuba tank?
Your local scuba shop, Ebay, and other online stores are good sources for scuba tanks. When buying used, keep in mind that scuba tanks must be hydro'd and visually inspected on a periodic basis. A used scuba tank may have a limited service life.
How many fills will I get off a scuba tank?
That all depends on the size (in cubic feet) and pressure of the supply tank and the size (in cubic inches) and pressure of the tank being filled. Two excellent resources are this chart
and this Java-driven calculator
Where can I get my scuba tank filled?
This will depend on your area. Scuba shops are an excellent choice, though some may require that you be a certified diver before they'll fill your tank. Other places to talk to are your local compressed gas supplier or a welding supply shop. In some cases, I've also heard of fire departments being willing to fill scuba tanks. You may also be able to work out a deal with a field/store owner.
How much should I expect to pay to fill my scuba tank?
That'll depend on where you get it filled. Prices ranging from $5 to $30 are not unusual.
Bare Bones System
A bare bones sytem will consist of a single scuba tank and fill adapter (commonly referred to as a yoke).
Frequently Asked Questions--Bulk Tanks/Cascade Systems
There are two ways to fill from bulk tanks--the single tank method and the cascade method. Common to both systems is the need for a fill station and a regulator. The fill station will provide the connection between the supply tank and the fill tank, while the regulator will control the maximum pressure to the fill tank.
Single Tank Method
The single tank method is exactly that, filling a paintball tank using a single supply tank. Aside from scuba tanks, this is the cheapest system to set up.
The cascade system uses two or more bulk tanks to fill a tank. In a cascade system, each tank is connected to a main line, which supplies the fill tank. The tanks are opened one at a time, starting with the supply tank that contains the lowest pressure. Once the pressure between the supply tank and the fill tank equalizes, the valve is closed and the next tank is opened, stepping up the pressure. The process is repeated until the fill tank is filled.
The cascade system allows you to use more of the air volume supplied in the tank. Once a tank gets to pressures below 500 PSI, it is removed from the cascade system and a new tank is connected (becoming the highest pressure tank).
Where Can I Get Bulk Tanks?
There are two routes you can go. The first, and cheaper, route is to rent tanks from a compressed gas supplier or welding supply company. Typically there is a daily rental charge and fill charge associated with renting tanks. The advantage is that your supplier will typically deliver full tanks to your location.
The other option is to purchase your own tanks and take them to your supplier to have filled. Purchase prices for bulk tanks range from $350-$1000 per tank. This is more expensive to set up, but it will save you the daily rental and delivery charges.
Bare Bones System
A bare bones sytem will consist of a single bulk tank, rented from a gas supplier, and a fill station. When renting a tank, you'll want a 4500 PSI nitrogen tank. You can find these tanks through gas suppliers or welding supply companies.
Frequently Asked Questions--Booster System
A booster system is a machine that uses a larger volume of lower pressure air to compress a smaller volume of high pressure air, thereby increasing the pressure of the high pressure air. This is accomplished through the use of air driven pistons.
Boosters come in two styles--single action and dual action. A single action booster will have one high pressure piston and one low pressure piston. A dual action system will have two high pressure pistons slaved to a single low pressure piston. Dual action systems are more efficient and can support a greater number of fills per hour.
Bare Bones System
A bare bones sytem will consist of a single bulk tank, a shop compressor (100 - 150 PSI), and a single stage booster system. When renting a tank, you'll want at least a 2200 PSI nitrogen tank. You can find these tanks through gas suppliers or welding supply companies.