Chalk Calcium (Carbonate) is used in brewing to raise pH levels. Generally used in making dark beer to offset the acidity of dark malts. When making dark beers a higher carbonate level is considered to be a positive attribute of brewing water. Munich, Dublin, and London are examples of classic water sources that exhibit high calcium carbonate levels. Porters and Stouts are both beer styles that tend to benefit from higher calcium carbonate levels in brewing water.