Draft beer systems may seem somewhat complicated at first glance. But once you understand the basics, you’ll see that they’re actually quite simple systems. From keg pressure settings and standard definitions, to keg dimensions and pouring techniques, you’ll find some answers here. Quench your thirst for knowledge and become a smarter, more educated draft beer connoisseur.


Glossary of Draft Beer Terms

Draft Beer

Any type of beer that is drawn from a large vessel. Kegs aren’t the only “vessels;” the term “draft beer” includes cask ale as well.


Metal container used for storing and dispensing pressurized liquids. A single hole centered at the top of the keg and a two-way valve allows liquids to be added and removed from the keg.

Keg Beer

Unpasteurized beer that is dispensed from a keg using gas pressure.

Direct Draw Draft System (Standard Draft System)

Technical name for specialized equipment built specifically for dispensing keg beer from a temperature-controlled environment through the use of compressed gas. Direct draw draft beer systems may be housed in a kegerator, walk-in cooler, or converted refrigerator.


Keg Volume and Dimensions

Note: These measurements apply to standard US kegs. US keg dimensions may vary slightly by manufacturer and brewery. European kegs vary in size, but are similar to US sizes.

½ Keg

Holds 15.5 gallons – approximately 165 12-ounce bottles

Weighs 161 pounds when full

24″ high with a 16″ diameter

¼ Keg

Holds 7.75 gallons – approximately 82 12-ounce bottles

Weighs 87 pounds when full

12-13″ high with a 16″ diameter

1/6 Keg

Holds 5 gallons – approximately 54 12-ounce bottles

Weighs 55 pounds when full

24″ high with an 11″ diameter


The Basics of Keg Pressure

Pressure is an imperative component of all fully-functional draft beer systems. It’s what keeps your beer carbonated and tasting fresh all the way from keg to glass. Having too much or too little pressure will affect the way your beer is dispensed, and you won’t be able to enjoy its full potential. These keg pressure pointers will help you find that perfect medium.

About Head Space

As CO2 enters a keg, it displaces your beer at a constant pressure. When you open the tap/faucet, beer flows out of the keg and into your glass due to a push from the CO2. The gas then fills the space where the beer was formerly housed, and that’s the “head space.” The CO2 fills the head space and maintains the pressure inside of the keg at the PSI set on your regulator. This constant PSI keeps the beer carbonated by preventing CO2 leakage.

Keep it Straight

Your CO2 tank must be stored upright or it won’t work properly. Storing the tank improperly can also cause expensive damage to your regulator.

Find the Magic Number

Most ales and lagers produced in the US should be dispensed at 10 – 12 PSI. Stout and other nitrogen-reliant keg beers are usually dispensed at 25 – 30 PSI.

For the specific dispensing pressure for a particular keg, check with your local beer distributor.

Too Much Pressure

Too much pressure will leave you with foamy beer that comes quickly out of the faucet. If your beer is over-carbonated, the foam will appear tight with large bubbles.

If you encounter this problem, it’s easy to fix. Adjust your regulator pressure to the proper lower level and draw a few foamy pitchers. You can also use your coupler’s relief valve to bleed out the extra pressure. These measures will force your system to balance itself out again.

If the pressure is left too high for too long, CO2 will be forced into the beer resulting in permanently over-carbonated and excessively foamy beer. Thus, it’s important that you address this problem as soon as the issue is identified.

Too Little Pressure

Too little pressure will also force foam because the CO2 can break free from the beer as it enters your glass. If the pressure is not raised to the appropriate level, your beer will eventually become flat.

When you see foam or bubbles visibly rising in your beer hose, this is a telltale sign of low pressure. If your beer is under-carbonated, the foam will look loose, often described as appearing “soapy” with small bubbles.

To correct low pressure, first check to make sure your CO2 tank isn’t empty and that it’s turned on. This seems like a “duh” suggestion but sometimes it’s the simplest issue that causes the problem. Next, check your regulator to be sure it’s set at the right level. If the tank is functioning and there aren’t any obstructions in your gas line, and your regulator is set to the correct PSI, then most likely your regulator or gauge needs to be replaced. Unfortunately, regulators do wear out and typically need to be replaced every 4-6 years or so.


Keg Tips, Tricks, and Rules to Remember

Keep it Calm

After any sort of transport or travel, give your keg some time to settle down. If you don’t, you’re likely to experience excessive foaming at tapping time. Remember that the beer inside of a keg is carbonated, so moving or shaking it will cause it to foam – just like a can of beer or soda. We recommend that you let your keg sit for an hour or so after transport.

Keep it Cold

Keg beer is unpasteurized, so it has to stay cold to stay good. As a general rule, think of keg beer as you think of milk: it needs to be refrigerated at all times. Keep your kegs between 34 – 40 degrees Fahrenheit and your beer will remain fresh and delicious.

Keep it Fresh

The beer inside a keg will retain its full flavor about 30 – 45 days after tapping. It’s difficult to pinpoint an exact amount of time, as a keg’s “shelf-life” is dependent on storage conditions and the brand/style of the beer. Generally, hoppy beers and those with a higher alcohol content will last longer because the hops and alcohol act as preservatives, inhibiting the growth of bacteria.

Keep it Clean

When beer does go bad quickly, it’s almost always one (or both) of two culprits: oxygen and/or bacteria. Unfortunately, bacteria will eventually spoil unpasteurized keg beer – even when the keg is kept in the perfect storage conditions.

Modern scientists have discovered that the only way to beat the bacteria is to drink all of the beer in your keg, before the bacteria has a chance to ruin it – usually in that 30 – 45 day range.

The other culprit, oxygen, is particularly harmful to kegs tapped with a hand pump. A hand pump forces air (containing oxygen) into the keg, which in turn, forces the beer out. This is good. However, as soon as the oxygen is introduced in the keg, it causes the chemical reaction called oxidation.

Oxidation will cause the beer inside of a keg to go flat and acquire a sort of sour taste. Thus, a keg tapped with a hand pump should be consumed within 24 hours. Thankfully, neither of these processes render beer harmful to humans, but they do make it undrinkable.