|Common Brewing Minerals|
Although you may have learned that pure water is H2O, water for brewing must contain much more. Not only do dissolved minerals and ions affect the taste of ingredients in beer, they also provide necessary nutrients for growing yeast and buffering reactions relating to the pH of the water and the grains. Common dissolved minerals found in brewing water include:
Water from different sources around the world have different concentrations of these minerals that are naturally dissolved in it. The water found in Burton, England has a different profile from the water found in Pilsen, Czech Republic. These differences in water is what partially led to different styles of beer. Pilsner beer became possible due to the extremely soft water found in Pilsen, while the sulfate content in the water around Burton favored hoppy beers that became what we know as Pale Ale.
The rule of thumb is that if your water tastes okay to drink then it will be okay to brew with. Tap water can however contain high levels of chlorine or chloramine, especially from municapal sources, that can lead to off flavors.
Bottled Spring Water
Bottled spring water is generally fine to use in many beer styles, however one never knows truly what is in the water. Spring water, being from a ground source can be particularly hard. In addition, many bottlers use multiple sources for their water, resulting in variation in mineral content from shipment to shipment. Many manufactures publish water profiles, but often these profiles have such a wide range in the potential mineral content that the profile is often generally useless to a brewer.
Distilled water has has all mineral content stripped from it in a distillation process. It is not recommended for brewing all-grain beer because some minerals are necessary for healthy fermentation. Distilled water is fine though for extract brewing because minerals from the extract manufacturer's water are already in the extract. Distilled water is also useful for diluting hard tap water.
Reverse Osmosis water, also called RO water, is generally the same as distilled water, only the water has had the minerals removed by passing it through a membrane instead of a distillation process. RO water can be used for brewing the same as distilled water.
Water can be treated in a variety of ways to affect mash pH, and ultimately, final beer flavor.
Chlorine can be evaporated from water simply by letting it sit out overnight, by dissolving a campden tablet (1 tablet treats 20 gallons), or by using charcoal filtration.
Chloramine is a more common compound found in municipal water systems, and can be removed by dissolving a campden tablet (1 tablet treats 20 gallons), or by using charcoal filtration.
Salt and Mineral Additions
- Baking Soda - Sodium Bicarbonate
- Chalk - Calcium Carbonate 
- Gypsum - Calcium Sulfate 
- Table Salt - Sodium Chloride 
- Calcium Chloride - 
- Epsom Salt - Magnesium Sulfate 
Even though water is usually considered one of the basic ingredients of beer, some adventurous home brewers have tried replacing brewing water with other liquids. Almost any water-based liquid can theoretically be used in brewing, and can contribute flavor, fermentables, or both. Examples that have been tried, and reported as successful by their brewers, include everything from unconcentrated maple sap to Mountain Dew.