This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
As to water used for these beers, it is hardly necessary to say that the very best spring water usually gives the best of results, and such waters, diluted with foreign matters and sub-stances, or otherwise contaminated, must strenuously be avoided. Where the spring water is not obtainable, and common well, river or pond water must be depended upon, an effective filter should be made use of, which not only removes those substances visible to the naked eye, but also those invisible, minute, microscopical substances, which remain in water in a diluted state even after it appears to be as bright as crystal. That can be removed only by creating a chemical change of action.