A half-barrel keg of beer weighs 140 to 170 pounds. It holds 15.5 gallons, which is about seven cases of beer. Keg sizes are not standardized, so volumes and measurements can vary slightly between countries and manufacturers.
A keg can be tapped with a gas tap or party pump. A party pump exposes the beer to outside air, which causes oxidization and bacteria. If a party pump is used for tapping, a keg of beer will last about 18 to 24 hours before its taste starts to spoil. A gas pump can keep a keg good for up to 120 days under proper refrigeration. Kegs are normally used with a bucket and ice to keep the beer cold.