How Draught Beer Dispense Systems Work

A draught beer dispense system is made up of a few core components: the keg itself, a gas supply, a regulator, beer lines, and a tap or font where the beer is poured. Understanding how these parts interact helps explain why two venues serving the same beer can produce noticeably different results.

The role of gas

Beer in a keg needs to be pushed out under pressure, since it cannot simply be allowed to flow by gravity in most commercial settings. This is done using a gas cylinder connected through a regulator, which controls how much pressure is applied to the keg. The choice of gas affects both how the beer pours and how it tastes.

Pure carbon dioxide is commonly used for beers that are naturally carbonated with carbon dioxide, since it maintains the existing carbonation level without adding other gases into the liquid. A blended gas, usually a mix of carbon dioxide and nitrogen, is often used for beers that benefit from a smoother texture and tighter, longer lasting head. The nitrogen does not dissolve into the beer as readily as carbon dioxide, which is part of why nitrogen based pours tend to look and feel different in the glass.

Pressure and balance

Every dispense system needs to be balanced, meaning the pressure applied by the gas has to suit the length, diameter and rise of the beer line between the keg and the tap. If the pressure is too high for the line length, the beer will pour too fast and foam excessively. If it is too low, the pour will be slow and may end up flat, since not enough pressure is being maintained to keep the beer properly carbonated as it travels.

This is why longer beer lines, such as those running from a cold room to a bar some distance away, often need either a higher operating pressure or a wider line diameter to compensate for the added resistance, while short runs need much less pressure to achieve the same result. There is no single correct pressure that applies to every setup, since it depends entirely on the physical layout of the lines.

Temperature control along the line

Good dispense systems are designed to keep the beer at a consistent temperature from the keg all the way to the tap. Many systems use some form of cooling along the beer line itself, not just in the cold room where the keg is stored, because a line that runs through a warm space can heat the beer enough to cause problems at the tap even if the keg itself is cold.

Where this cooling is inconsistent, it often shows up as foaming at the start of a pour, when the beer in the line has warmed slightly while sitting unused, followed by a more normal pour once the warmer beer has cleared the line.

The tap and font

The final part of the system is the tap itself, sometimes mounted on a font that may also be cooled. The tap controls the flow of beer as it is poured, and its condition matters: a worn or dirty tap can introduce air into the pour, causing extra foam, or can restrict flow in a way that changes how the beer behaves compared to a clean, well maintained one.

Fonts and taps are also where most of the visible cleaning and maintenance happens, since they are handled constantly and are the most exposed part of the system to the open air.

Putting it together

None of these elements work in isolation. A correctly chosen gas blend, a properly balanced pressure for the line length, consistent cooling, and clean, well maintained taps all need to be in place together for a draught system to reliably produce a good pour. When something is wrong with a glass of draught beer, from too much foam to a flat, lifeless pour, the cause can usually be traced back to one of these specific points in the system rather than to the beer itself.