Brewing water can be pretty confusing, especially to a new homebrewer who is starting to brew all-grain batches. All you need to know in the beginning, however, is if six certain ions in your water are in the proper range, which you can easily find out from reading a water report.
If you live in a place that has municipal water, you can request a water report from your department of public works. If you are using spring, well or some other source of tap water you won’t have a public water report, but you can have it similarly tested for its content.
Water reports intended for the general public are typically expressed in parts per million (ppm), which is defined as one milligram of the substance per liter (1 mg/L).
The six important ions in water that you need to know about for brewing are: calcium, magnesium, bicarbonate (or total alkalinity as CaCO3), sodium, chloride and sulfate.
• Calcium should be in the range of 50–150 parts per million (ppm). Calcium is an ion that makes water “hard,” and it is important for many yeast, enzyme and protein reactions. Hardness is a measure of the calcium and magnesium content in water. When there is an equal amount of calcium and bicarbonate present, it is known as “temporary hardness,” which can be reduced by boiling. Permanent hardness is measured by the amount of calcium that can’t be removed by boiling. Water hardness is neither good nor bad, depending on what style of beer you want to brew. For example, temporary hardness is good for dark beers and permanent hardness is good for brewing pale ales. Research the style of beer that you want to brew to figure out if the hardness of your brewing water is appropriate for what you want to brew.
• Magnesium should be in the range of 0–30 ppm. It also contributes to water hardness and is a yeast nutrient. Magnesium is best kept at small amounts because it can contribute off/bitter/metallic flavors to the beer. Magnesium can also give food and beverages a laxative effect, which is another reason to limit this ion in brewing water.
• Bicarbonate should be 0–250 ppm – or if your report reads as “total alkalinity” it should be in the 0–200 ppm range. More specifically (according to John Palmer’s How To Brew), bicarbonate should be 0–50 ppm for pale, base-malt only beers. 50–150 ppm for amber colored, toasted malt beers and 150–250 ppm for dark, roasted malt beers (these levels assume calcium in the range of 50–100 ppm to balance the alkalinity of the bicarbonate). Bicarbonate affects the pH of your water. A high pH in the mash can cause poor extraction rates, darken the wort, and leach more tannins into your mash.
• Sodium should be between 0 and 150 ppm. Sodium in moderate levels can accentuate malt flavor.
• Chloride can be anywhere between 0 and 250 ppm. Chloride is similar to sodium in that it can accentuate malt flavor if it is in a moderate range. If there is too much chloride, however, the beer can suffer from off flavors.
• Sulfate should be around 0 to 150 ppm. Sulfate can accentuate hop bitterness in moderation, but too much can make the bitterness seem harsh.