Draft beer is the best of the brewer’s art, and serving it cold and fresh is the best way to enjoy it. At half the cost of cans and bottles, keg beer is also your best value, and it’s easy to dispense – whether you’re at home or a bar or restaurant.
Let’s talk about the basic components of a draft beer system. It’s always best to start at the keg and move to the glass.
Today’s beer kegs are made of stainless steel. The modern single valve (sometimes referred to as Sankey) keg has a single opening on the top. A tube called a "spear" extends from the top of the keg to the bottom. There is a sump or shallow well at the bottom to ensure as much beer is emptied out of the keg as possible. This self-closing valve on the top is opened (tapped) with a keg coupler. The valve allows gas (usually carbon dioxide, CO2) to push the beer out of the keg.
Most U.S. brewers sell beer in 1/2 barrels of 15.5 gallons, 1/4 barrels of 7.75 gallons, and 1/6 barrels of 5.17 gallons. In the U.S. the terms half-barrel and quarter-barrel are derived from the U.S. beer barrel legally defined as being equal to 31 U.S. gallons.
A keg coupler is like a “key” and it fits the keg valve which can be thought of as the “lock.” The keg coupler attaches to the keg valve and to a gas line running to the CO2 regulator and tank. “Tapping” the coupler into the keg allows the compressed gas to enter the keg and push out the beer. In order for beer to be dispensed, the valve needs the corresponding type of coupler that fits. The type of coupler depends on the specific beer keg. For example, the American Sankey “D” System coupler is easily the most popular. It fits all domestic brand kegs, as well as 95% of American beers.
CO2 Gas Cylinder (Tank)
A CO2 tank is made of aluminum, but has different valves depending on the gas stored (i.e. CO2 is the CGA 320 valve, Nitrogen is the CGA 580 valve). One 5lb. CO2 tank holds enough gas to dispense 5-7 kegs. This ratio holds true for larger CO2 tanks as well. Therefore, a 10 lb. tanks will dispense at least 10 kegs, and a 20 lb. tank at least 20 kegs.
CO2 Gas Regulator
Before you start, make sure the CO2 regulator is securely attached to the CO2 cylinder. The CO2 tank contains approximately 800-100 PSI – this needs to be regulated down to a useable pressure. Most CO2 regulators have a screw on the front of the device which allows the outlet pressure to be set. Using a flathead screwdriver slowly adjust the pressure - turning the screw clockwise allows more pressure, while rotating the adjustment screw counter-clockwise lowers pressure. Small turns of the screw can have a big result, so be careful as you adjust.
CO2 Gas Line
Please note that we never refer to the gas for draft beer as “air” – never use an air compressor to dispense draft beer. Air compressors are never as clean as CO2. The gas line connects the regulator to the keg coupler. Using 5/16”ID gas hose, clamp each end securely to ensure the pressurized gas does not escape and create a leak.
In a direct draw beer system (approximately 5’ run from keg to faucet) the beer line is only 3/16” ID. This narrow diameter along with the length of tube is known as restriction. Only use a vinyl hose that is approved for beverage dispensing, and preferably brewery approved. In general, the longer the beer line is, the lower the serving pressure at the faucet. If the faucet outlet pressure is too high or too low, the overall system is said to be out of balance and your beer will either foam or be flat.
Often referred to as the “tap” the function of a faucet is to dispense the beer into the serving vessel.
As the last component in the system, the faucet’s mission is to direct the flow of beer and ensure the perfect pour. The standard U.S. beer faucet is designed to dispense a wide variety of beer styles, including all American ales and lagers.
Typically rear-sealing, the standard U.S. faucet comes in a variety of shapes, and materials. Most faucets are forged brass and then chrome plated, this type will give years of service before the chrome wears off. The material preferred by commercial users and brewers is 304 grade stainless steel for its ability to not impart off tastes and its resilience to harsh cleaning chemicals.
Standing upright and connected to the faucet is the tap handle or marker. The tap handle is merely the lever which opens the beer system allows the beer to flow out of the faucet. The primary use for a handle in commercial on premise setting is to identify the beer on tap.