A keg is a small barrel.
More recently, a keg is often constructed of aluminum or steel. It is commonly used to store, transport, and serve beer. Other alcoholic or non-alcoholic drinks, carbonated or non-carbonated, may be housed in a keg as well. Such liquids are generally kept under pressure.
Beer keg 
Beer kegs are made of stainless steel, or less commonly, of aluminium. A keg has a single opening on one end. A tube called a "spear" extends from the opening to the other end. There is a self-closing valve that is opened by the coupling fitting which is attached when the keg is tapped. There is also an opening at the top of the spear that allows gas (usually carbon dioxide) to drive the beer out of the keg. The coupling fitting has one or two valves that control the flow of beer out of and gas into the keg. The keg must be in the upright position, that is, with the opening on top for the beer to be dispensed. Kegs can be contrasted to casks, which have two or more openings and no spear.
Historically a beer barrel was a standard size of 50 gallons, as opposed to a wine barrel at 32 gallons, or an oil barrel at 42 gallons. Over the years barrel sizes have evolved and breweries throughout the world use different sized containers. Even when the content capacity of two kegs are equal—e.g. metricized to 50 liters—the keg shape and keg tap system may differ heavily.
U.S. keg sizes 
Most U.S. brewers sell beer in 1⁄2 barrels of between 14 and 16 gallons, 1⁄4 barrels of between 7 and 8 gallons, and 1⁄6 barrels of between 5 and 6 gallons.
Since keg sizes are not standardized, the keg cannot be used as a standard unit of measure for liquid volumes. This size standard varies from country to country and brewery to brewery with many countries using the metric system rather than U.S. 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 (this is not the same volume as some other units also known as barrels). A 15.5 U.S. gallon keg is also equal to:
- 12.7 Imperial gallons
- 58.67 liters
- 103.25 Imperial pints
- 124 U.S. pints
- 496 U.S. gills
- 165 twelve fluid ounce (U.S. measure) drinks
- About 90 bombers (22 fl oz bottles)
- About 6.88 24-unit cases of 12 fl oz cans
- About 5.5 30-racks of 12 fl oz cans
- 1,984 fluid ounces (U.S.)
However, beer kegs can come in many sizes:
|Size (US gal)||Size (liters)||No. of 12 fl oz drinks||No. of 16 fl oz drinks||No. of 20 fl oz drinks||Weight of full keg (lb)||Also known as|
|1.32||5||14||10.6||8.5||—||Mini Keg / Bubba (single-use/recyclable)|
|5||18.9||53||40||32||55-60||Soda syrup / Corny Keg / Home Brew|
|5.17||19.8||56||42||33||58-60||Sixth Barrel / Torpedo Keg / Sixtel|
|6.6||25||70||50.25||42||—||"Half Barrel" (Europe)|
|7.75||29.3||82||62||49||90||Quarter Barrel / Pony Keg|
|9.2||35.15||99||74||59||—||Wall ("99 Bottles of Beer")|
|13.2||50||140||105||84||—||Import Keg (standard European "Barrel")|
|15.5||58.66||165||124||99||140–170||Half Barrel / Full Keg|
DIN-keg and Euro-keg 
In European countries the most common keg size is 50 liters—this includes the UK with its non-metric keg system where the standard keg of 11 imperial gallons is almost exactly 50 liters in the metric system. The German DIN 6647-1 and DIN 6647-2 have also defined kegs in the sizes of 30 and 20 liters. A newer Euro regulation defines 50, 30, 25 and 20 liters where the keg shape is usually thicker but not as tall as the German keg specifications.
|content||DIN 6647-1/-2||DIN-Keg Diameter||Euro-Keg||Euro-Keg Diameter|
|50 L (13.21 gal)||600 mm (high)||381 mm (ø steel keg)||532 mm (high)||408 mm (ø steel keg)|
|30 L (7.93 gal)||400 mm (high)||381 mm (ø steel keg)||365 mm (high)||408 mm (ø steel keg)|
|25 L (6.61 gal)||-||-||327 mm (high)||395 mm (ø steel keg)|
|20 L (5.28 gal)||310 mm (high)||363 mm (ø steel keg)||216 mm (high)||395 mm (ø steel keg)|
In some areas it is common to refer to the size not in liters but in beers. In areas such as Germany, where the standard beer size is 0.5 liters, that means a 50 liter keg contains 100 beers.
Specifications for a U.S. 1/2 barrel keg 
Accepted specifications for a standard keg are:
|Height of keg||23.3 inches|
|Diameter of keg||16.1–17.15627 inches|
|Contents||1984.0 U.S. fluid ounces|
|15.5 U.S. gallons|
|12.91 imp. gallons|
|Full keg weight||160.5 pounds (72.8 kg)|
|Empty keg weight||29.7 pounds (13.5 kg)|
|Beer weight||130.8 pounds (59.3 kg)|
|24 × 12 fl oz case equivalent||6.9 cases|
|12 fl oz servings||165.6|
|16 fl oz (1 U.S. pint) servings||124|
Tapping a keg 
There are two different types of tapping equipment that are available for kegs: party pumps and gas taps. Party pumps utilize outside air, thus introducing oxygen and bacteria into the keg. This causes the beer to oxidize, giving it an unpleasant taste comparable to wet cardboard. Kegs operating a party pump should be used within 18–24 hours so that the beer does not become unpalatable. Gas pumps normally use CO2, but certain brewers require a mix of other gases (Guinness requires 25% CO2 and 75% nitrogen). Gas pumps can preserve a keg up to 120 days with proper refrigeration.
As with any pressurized container, a keg can cause injury, even at normal operating pressure, whether with compressed air or carbon dioxide:
"The tapping system and pressure regulator both should be equipped with a pressure relief (blow off) device. If you are not familiar with tapping equipment, consult your retailer..." (printed on an Anheuser-Busch's keg cap)
In the US and Australia, kegs or beer coils are usually kept in a bucket of ice and/or water to keep the beer cool.
Other types of kegs 
Cornelius keg 
Cornelius kegs were originally made by the IMI Cornelius Company. Since the arrival of newer technology such as Bag-In-Box (BIB) packages soft drink bottlers have mostly abandoned their Cornelius kegs, often making them available to hobbyists.
Mini keg 
The mini keg is a 5-liter keg produced for retail sales. Some brands come with a spout and pour from the bottom via gravity, while others may use a low cost pressurized tap. Mini kegs are typically not returned to the manufacturer for cleaning and refilling. The kegs, being made of aluminum, may be recycled.
In Canada, Molson brewery dubbed the mini keg "Bubba". This name has now been genericized to generally apply to all 5-liter mini kegs in Canada. This might cause confusion, as a company called Bubba Keg is established in the U.S., and appears to not be associated with Molson. Today, mini kegs are widely available in liquor stores worldwide, with Heineken, Grolsch and Bitburger all adopting the design.
Beer ball 
Another type of mini keg is the "beer ball" or the "party ball", a disposable plastic ball that usually holds around 5.2 gallons, roughly the equivalent of 55 twelve-ounce beers, though they can also be found in a smaller 3.8 gallon size. Like kegs, it is necessary to tap the ball before the beer inside can be served.
Oneway kegs 
Another type of keg is the "oneway keg" which is now available in most global markets. Ecokeg, an Australian invention, provides one way kegs that are mostly recyclable and much lighter than steel kegs. They provide kegs in 30 L and 38 L sizes only with two outer options plastic or reinforced cardboard BoxKeg. The PubKeg, manufactured by Rehrig Pacific Company, is another oneway keg available on the market. The PubKeg comes in a 20 L size and is completely recyclable. Other oneway kegs on the market are keykeg, Schaeffer aluminium keg & Expodraft from Cardiff group nv with a patented double bag system, available in 10L, 20L and 30L.
Quarter barrel (pony keg) 
A quarter barrel, more commonly known as pony keg, is a beer vessel containing approximately 7.75 U.S. gallons (29.33 liters) of fluid. It is half the size of the standard beer keg and equivalent to a quarter of a barrel. It will serve roughly 82 twelve-ounce cups. The shape of a pony keg resembles that of a full-sized keg, while being much easier to move manually. However, it shares many inconveniences with the bigger kegs, such as: often requiring a deposit when purchased; needing a tap to serve the contents; and posing difficulties in determining the amount of beer remaining (weighing the keg or observing its buoyancy are common techniques). Despite this, a pony keg can be a cheap way to provide beer for a medium-sized party.
Sixth barrel 
A sixth barrel keg is becoming the choice for many establishments and breweries that wish to use kegs smaller than a half barrel. The sixth barrel kegs are nominally larger in size and volume compared to the Cornelius keg. They are normally fitted with a standard US Type D Sanke coupler on a single downspout; whereas, Corny kegs are normally fitted with a flip-hatch, and a dual connector pin-lock or ball-lock top. Although the sixth barrel torpedo keg is approximately the same height as the standard half barrel, the smaller foot print of the sixth barrel allows retailers have a greater variety of beer in a small space. This size keg is quickly replacing the quarter barrel size which has the same foot print as a half barrel keg, but is only half as tall. Other than smaller circumference, sixth barrel kegs are very similar to their full-sized counterparts in construction. A stainless Micromatic brand sixth barrel keg weighs approximately 14-15 pounds (6.3-6.8kg) when empty, and approximately 58-60 pounds (26.3-27.2kg) when full.
Eighth barrel 
An eighth barrel has the same dimensions as a sixth barrel, but the bottom 7 inches are hollow.
UK and Irish keg supply structure 
The beer vessel supply structure in the UK and Ireland is quite different, whilst the couplers for kegs have been largely standardised to sankey, grundy and interbrew, a couple of others exist such as UEC and U-Type; however these are much less common. The kegs themselves are made from stainless steel or aluminium. The standard keg size is 11 imperial gallons (50 liter/88 imperial pints approx) and the vast majority of keg beers are supplied in this keg size. There are also smaller 30 liter (54 imperial pints approx) kegs usually reserved for more specialist and/or premium European beers.
A number of manufacturers also produce 18 imperial gallon (approximately 82 liters/144 imperial pints) and 22 imperial gallon (approximately 100 liters/172 imperial pints) kegs, however owing to their size they are not so popular as manual handling is seen by some to be difficult, and as a result they tend to be used only for large scale events and bars with high throughput.
For bars that sell an excessive volume of beer there is the 36 imperial gallon (150 liter/260 imperial pint) keg, however due to its very large size few people can move them making it an impractical choice.
Keg laws 
In the U.S. as of 2005, there are 21 states and numerous localities that have keg registration laws. The laws vary widely in terms of whom they target, what their intended purpose is, and how strongly they are enforced. Most major breweries now use internally speared kegs.
See also 
- "Old Sturbridge Village FAQ". Retrieved 2007-10-29.
- Briggs, D. E.; Boulton, C. A.; Brookes, P. A.; Stevens, R., Brewing, Science and Practice, CRC Press, ISBN 0-8493-2547-1
- "keg". Merriam-Webster Online Dictionary. 2004. Retrieved 2007-06-21.
- 27 CFR § 25.11.
- "Retailers Guide to Draft Beer Dispensing". Retrieved 2007-10-29.
- Soroka, W, Fundamentals of Packaging Technology, IoPP, 2002, ISBN 1-930268-25-4
- Yam, K. L., Encyclopedia of Packaging Technology, John Wiley & Sons, 2009, ISBN 978-0-470-08704-6
- How to Tap a Keg—A wikiHow article
- Keg Beer Dispensing Articles and Education
- How to remove and reassemble the valve in a sanke keg