What is a common cause of flat beer related to system pressure?

Flat beer is commonly associated with too low system pressure. When the pressure in a draft beer system is insufficient, the carbon dioxide that is dissolved in the beer can come out of suspension more easily. This results in less carbonation in the beer, which means it will have a flat taste and mouthfeel. Proper system pressure is vital because it helps maintain the balance between the beer and the carbon dioxide; if the pressure is too low, not only does the beer lose its proper fizziness, but it may also impact the overall flavor experience.

In contrast, high system pressure could lead to over-carbonation, which typically causes excessive foaming rather than flatness. Dirty glassware and warm beer temperature can also affect the beer's presentation and enjoyment but do not directly cause the same issues related to carbonation levels linked to system pressure.