kegs

Kegs are large, pressurized containers used to store and dispense beverages, most notably beer. Typically made of stainless steel or aluminum, a keg is a sealed cylindrical vessel with domed ends and fittings at the top for filling and tapping. The interior is designed to withstand CO2 or mixed-gas pressure that pushes the beverage through a tap line.

Common sizes vary by market. In commercial beer service, the half-barrel keg holds 15.5 gallons (58.7 liters). Smaller options include the sixth-barrel keg (about 5.16 gallons, 19.5 liters) and the quarter-barrel or pony keg (about 7.75 gallons, 29.3 liters). The Cornelius keg, a 5-gallon unit, is widely used by homebrewers and portable systems.

Kegs connect to tap systems via fittings and couplers. In the United States the standard beer keg uses a Sankey (D-system) valve; in other regions other valve types are used. Kegs are typically pressurized with CO2 or a CO2–nitrogen mix to maintain carbonation and drive beer to the tap.

History and use: Metal kegs largely replaced wooden barrels in the 19th century and have since become reusable components in brewing and hospitality. They are commonly leased or owned by breweries and events and are used for other beverages as well, including cider, wine, and kombucha, where gas pressure helps maintain carbonation and controlled pouring.