- $127 for six-hour drink trailer rental ($250 value)
Beer Kegs: Inside the Stainless-Steel Party Staple
American, German, and English beers all have different tappers. Learn why with Groupon’s examination of how beer kegs work.
When we go to a restaurant and order a draft beer, we take it for granted that we’ll get a cold drink that doesn’t have too much foam or taste flat. But a lot of science goes into making sure a customer gets the perfect pour from a keg. Stainless-steel kegs are airtight, which keeps the beer from becoming flatter than a pancake stretched over Kansas. Inside a keg, a long metal tube called a spear reaches from the top of the keg almost to the bottom. Beer travels up from the bottom of the keg through the spear and out through the tap at the top.
The beer defies gravity and flows out of the tap with the help of pressure. The average party keg uses the aptly named party pump to pump air into the keg and create pressure. When this tap is pumped a few times, it builds up enough air pressure to force the beer up and out of the tap. This air pumped into the keg kills the beer’s flavors and aromas over time, and the beer goes flat in a day or two. So though a party tap works for frat parties and jury meetings, it is not an option for a restaurant, which might take several weeks or months to go through a single keg.
Restaurants feed pressurized CO2 or nitrogen, depending on the beer, into the keg at a constant rate to maintain the pressure inside. A specialized tap called a coupler, designed for kegs pressurized with gas, pumps the beer out of the keg. There are different types of taps for American beers, German beers, and English beers, because different beers need different amounts of pressure thanks to differences in aroma and flavor. More aromatic and flavorful beers are less carbonated, so they need less pressure to maintain their low carbonation level—hence, the different tap systems.