How Does a Keg Tap Work?

Purpose of a Keg Tap

A beer keg tap is a valve that regulates the release of beer. The keg tap is used by pressing or pulling a lever, which opens and releases the flow of beer. The tap works by releasing the pressure built up in the delivery line connected to it. The pressure is what pushes the beer up and out of the keg and into a container. The tap either prevents or aids the flow of the beer. Technically a tap is an on-off or open-close switch.

In a typical bar setup a pressure dispense system delivers beer when someone pulls the tap handle and opens the tap valve. The pressure behind these beer keg taps is supplied by a canister of carbon dioxide (CO2) connected to each keg. Via a single tube (separate from the CO2 connection), the keg is connected to the dispensing system. The tube connects to one valve (tap), which in turn is connected to one handle in a series of handles. In very complex dispensing systems the pressure may be provided by a combination of CO2 and nitrogen.

In a portable system the same kegs used in a pressure dispense system can be tapped without CO2. These kegs receive their pressure via a single unit pump and tap combination often called a "party pump." The beer keg tap unit is separate from the keg. Once the pump is attached, the faucet on the pump must be opened to release the natural pressure in the keg. Pumping puts air pressure into the keg, and a push on the handheld lever (the beer keg tap handle) releases beer. Portable dispensing must be completed in one day because once the air is mixed with the beer, the beer begins to lose flavor and go flat.

Traditionally brewed beers and ales use an on-off valve. Using an on-off valve is called "serving by gravity" because there is no air pressure or gas added. The valve is pushed or hammered into the the keg and simply turned or pushed to open the keg or close it. Cask ale used in a pub usually has a beer line attached to it that in turn is attached to a beer engine (a cylinder and piston mechanism) to pull the beer out of the cask and up to the dispenser. Pulling forward on the lever or tap handle pulls beer out of the cylinder; pushing back on the handle pulls more beer into the beer engine cylinder from the keg.

The type of keg available will determine what type of keg tap should be used. American-style kegs are different from European-style kegs. Home-brewers often use a Cornelius keg, also called a Corny keg. In the U.S. there are seven different keg tap possibilities, each connected to a particular beer maker or type of beer. They are the D system (domestic beers), the S system (some imported beers), the A system (German beers), the G system (used by Bass, Caffery and Anchor Steam), the U system (English beers), Twin Probe (some microbreweries use this tap) and the Home Brew Coupler.