Once a keg of beer is opened, its shelf life depends heavily on the dispensing method and storage conditions. When we say a keg is “opened,” it means the keg has been tapped—either using a CO₂ system or a manual air pump—and beer is being drawn from it. From that point on, the clock begins ticking on how long the beer will remain fresh and enjoyable.

If the keg is connected to a CO₂ dispensing system, such as those found in restaurants, pubs, or home kegerators, the beer can last for up to 6 to 8 weeks after being tapped. The CO₂ keeps constant pressure inside the keg and prevents oxygen from entering, which is crucial in preserving both the flavor and carbonation of the beer. It is essential, however, that the keg remains properly refrigerated (ideally between 3–5°C or 37–41°F) and that the lines and taps are clean.

On the other hand, if the keg is tapped using a manual pump (often used for parties and events), air is introduced into the keg, which begins oxidizing beers. In this case, the beer should be consumed within eight to twelve hours, as it will quickly lose its freshness and may develop off-flavors.

For systems like the PerfectDraft machine, which use sealed, pressurized 6-liter kegs and hold the correct temperature, the beer can last for up to 30 days after being opened, offering an excellent balance between convenience and quality.

Regardless of the method used, signs that keg beer is going bad cover flatness, sour or metallic taste, or cloudiness. To maximize freshness, always keep the keg cold, avoid shaking, and serve through a clean, oxygen-free system.

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