- a Corny (or similar) stainless steel keg to hold the beverage. Various sizes are available but most common is the 19 litre 'Corny' keg.
- a CO2 (carbon dioxide) gas tank to pressurize the keg (for force-carbonation and dispensing),
- a gas regulator to lower the gas-tank pressure to a usable level,
- a hose with a quick-disconnect fitting to connect the CO2 tank to the Corny keg,
- and a hose with a plastic faucet or "picnic tap" and quick-disconnect fitting to dispense the beverage
The keg: Most kegs are 8-1/2 in. in diameter, about 26 in. tall, and hold 19 litre of liquid. The top and bottom ends of the kegs are covered with shock-absorbing plastic caps. The cap on the top end of the keg is molded to provide handles for easy lifting, although older kegs made by the Cornelius Company had no end caps at all but relied on a single metal handle bolted to the top. Your keg should have a pressure-relief valve in the lid -- an important safety feature.
Kegs are available with two types of valves, ball-lock and pin-lock, which refer to the method used to couple the hose fittings to the valves. The fittings are threaded slightly differently and are not interchangeable, so it's a good idea to pick one keg type and stick with it to avoid confusion. Ball-locks are more common are a bit easier to disassemble. Generally you will need at least two kegs so you won't have to finish one batch before kegging another.
CO2 tank: You'll also need a high-pressure CO2 tank to provide gas for carbonation and dispensing the beer. You may need to hire this piece of equipment.
Pressure regulator: You'll also need a single or dual-gauge gas pressure regulator for the tank, which is used to drop the gas pressure from the 800 phi or so in the tank to the 10-30 psi you'll need for force carbonation and dispensing The regulator is adjustable so you can set the output pressure to control carbonation levels and to control how the beer serves. Regulators include a pressure relief valve that will blow at or below the maximum pressure indicated on the low pressure gauge.
One or two gauges? Both single and dual-gauge styles work perfectly well. Both include a gauge that indicates the output (low) pressure setting, which is the most important information you need.
The dual-gauge unit also includes a second gauge that indicates the tank pressure, which tells you roughly how much gas is left. Knowing the tank pressure, though, is only marginally useful; it drops from 400 to 0 psi in what often seems to be the last few minutes of use. When the gauge says "almost empty," for all practical purposes, it's empty.
Connections: To connect the gas tank to your keg and to dispense the beer, you'll need two quick disconnects, a gas line, and a beverage line with a picnic faucet.
Disconnect fittings are available in both ball-lock and pin-lock styles to match the keg type.
To gain the most from your investment, use the flare-style outlet -- it's a short metal insert with a male thread. This style of fitting allows you to connect either pin-lock or ball-lock fittings to your regulator and even connect several kegs at the same time.