In-Line Carbonation, the process of dissolving carbon dioxide (CO₂) into beer as the beer is being pumped from one vessel to another. After fermentation is complete, beer will naturally contain some amount of dissolved CO₂. If this amount alone is not sufficient to give the beer its appropriate level of carbonation, in-line carbonation is often used to increase the CO₂ content of the beer to the desired level. This can be done whenever the beer is being pumped somewhere and is often done between the filter and the bright tank.

Factors affecting the efficiency of this process include time, temperature, pressure, and the size of the CO₂ bubbles being dissolved into the beer. High pressure and low temperature cause CO₂ to dissolve more readily in beer, so in-line carbonation is normally done at around 1 bar (15 psi) of pressure and near-freezing temperatures. Also, small bubbles of CO₂ and long contact time are critical for efficient dissolution. Diffusion stones or venturi jets are often used to produce the small bubbles necessary and are typically followed by a long section of pipe that allows the CO₂ adequate time to fully dissolve into the beer.

See also bright tank and carbonation.