Typically hard water as its higher mineral content is more agreeable to yeast than "pure" water. Distilled water is likely the worst unless minerals or mash are added. Either way removal of chlorine is a must and can be accomplished by an open lid "breather" simply allowing the water to breathe open air for a day, removal of chloramine is very difficult and if your metro water system has chloramine you should probably use distilled or spring water.
Avoid sulfurous water "skunk water" as some of the compounds the yeast or bacterias can generate could distill into some very vile compounds. --DGary 15:19, 13 February 2007 (PST)
Understanding Water Chemistry
- Bru'n Water Knowledge (Long but good, includes map of water hardness)
- Bru'n Water chemistry Calulator
Chlorine and Chloramine
In recent years, more water authorities have started to treat water with ammonia in addition to chlorine. This treatment results in the formation of chemicals called chloramines, which are similar to chlorine in that they kill bacteria and aquarium fish and ruin beer. Essentially, chlorine reacts with just about everything organic that it gets in contact with. That's how it makes your drinking water sanitary; it reacts with all the organic matter that any microbes could eat up, rendering them "unmetabolizeable". Also issues arise as yeast eat chlorine and chloramine and produce 'chlorophenols'. These phenols have extremely low taste thresholds; you can taste them even if they exist in only a few parts per billion. Your beer will have a difficult to define 'sharp' or chemical flavor, and usually a plastic or band-aid aftertaste, like you just stuck your nose into a first-aid kit. If the amount is low enough, you might only be able to taste it when you burp. There are several methods to removing Chloramines, some easier than others.
- MoreBeer: Removing Chloramine
- Chlorine-Chlorimine at Beer Geek
- Removing Chlorine and Chlorimine by use of Vitamin C
- By Products of Disinfection at Wikipedia
- Experiments in Removing Chlorine and Chloramine From Brewing Water(PDF)
- HowToBrew.com: Using salts for brewing water adjustments
- Morebeer.com: Treating Homebrew water (very detailed)
Some styles of washes are helped by specific water profiles. These profiles may accentuate or diminish certain flavor constituents to help mimic a certain style or brand of spirit.
- Water Profiles Note: "Mains" water means treated water from a municipal/commercial source.