I’ve been promising this talk for a long time, mostly because of the difficult nature of this topic. For a thorough understanding of this topic, do not read any of the commonly available homebrewing books. They are full of misinformation. The best source for detailed information is A.J. deLange’s Homebrew Digest posts.

I think most people will be happy to hear an easy approach that doesn’t take much chemistry and will work for them. This is the approach that I use and I find it to be quite successful. It is based on a set of assumptions about water chemistry:

• You must get rid of chlorine or chloramine.
• Some aspects of water chemistry are important for flavor, some are important for the reactions that go on in brewing (mashing, yeast flocculation, etc.).
• If you are an extract brewer, you only need care about flavor characteristics (unless you have some pretty nasty water).
• With modern materials and techniques, the only water issues we need to concern ourselves with as far as brewing reactions go are pH and [Calcium].

I will touch on these briefly. Note that unless you want to just start with distilled water you should get a water report. Mountain View sends these out every year and supposedly all municipal water suppliers must make this information available. Call your water department. If you live from Mountain View north, you are probably blessed with Hetch Hetchy water.

These compounds will combine with malt components to cause off flavors. Boiling or just plain sitting out overnight will get rid of chlorine, carbon filtering is needed to get rid of chloramine. To my knowledge, no one around here is receiving water with chloramine in it. People on Hetch Hetchy water will likely be switched to chloramine in 2-4 years.

All brewers need to control the levels of certain ions that affect beer flavor. Extract brewers should use soft tap water or deionized/distilled water as their extract already has the appropriate salts in it for most purposes. The exceptions would be to add some carbonate to generic extract (as opposed to a kit which presumably has the right salts) for continental dark lagers (say 0.5 g or 0.1 teaspoon baking soda per gallon) or "Burton salts" to a Burton pale ale (follow packet directions or use 1 g / 0.2 t epsom salt and 2 g / 0.4 t gypsum per gallon).

All grain brewers should follow the above advice but those with soft water may wish to increase the amounts by 25% or so to compensate for the lack of salts from extract assumed above. They may also wish to follow my policy that with soft water, a little NaCl should, according to theory, make things taste a little nicer. I use about 0.5 g or 0.1 teaspoon per gallon.

Note that I add the flavor salts to the boil to maximize control over how much makes it to the beer. All wort volumes refer to the final volume of the boil.

Now you want to control the pH and the [Calcium]. Exception: for some beers a soft water profile is desired. These include most Belgian beers and Pilsener. In this case start with soft water or a mix of tap and distilled and add nothing. First I will cover pH. I feel that pH paper is likely to be better than any pH meter you can afford. I prefer pHydrion brand. These are available in a wide variety of ranges and are accurate, which many pH papers are not. They are also cheap.

If, like me, you have to raise the pH to reach your optimum of 5.3-5.4, add up to 0.5 g or 0.1 teaspoon chalk (CaCO₃) per gallon to the mash. Note that the volume here still refers to the boil volume, since the flavor effect of these salts is your limiting factor. If you still need to raise the pH, add up to twice that much baking soda. In my experience this will work for all but the darkest beers, which I let stay a little below 5.3.

If you have to lower the pH, add up to 0.5 g or 0.1 teaspoon gypsum. Better than gypsum if you can get it is a flavor-neutral acid. A little lactic acid will work, but phosphoric or hydrochloric would be better. Add these carefully-they’re dangerous in concentrated form and a little goes a long way. Note that if you are lowering your mash pH you should lower your hot liquor pH as well. Much less acid should be required (gypsum will not lower your hot liquor pH) for this. If gypsum doesn’t do it you have hard water and should boil the night before and decant off the precipitate or use some distilled water.

Depending on what you did to adjust your pH, you may well have enough calcium. Subtract the amount of chalk or gypsum you have added from 1 g / 0.2 t per gallon and add the remaining amount in calcium chloride.