Water

Water is the biggest ingredient of beer: 85–95% according to the BJCP, about 95% according to the Brewers Association. In English breweries it has traditionally been called 'liquor'.

Natural water is almost never pure H2O. Water picks up minerals from the soil and rock it flows through. Those dissolved particles (ions) make the difference. Calcium and magnesium together make up the hardness. Bicarbonate determines the alkalinity: how much acid the water can neutralise. Those three mainly steer the acidity during brewing. Sulfate, chloride and sodium mainly act on the flavour.

A brewery uses much more water than ends up in the beer. In the US that is, according to the Brewers Association, an average of around seven litres of water per litre of beer; many craft breweries stay below three.

Water does two things in beer: it helps determine how the brewing goes, and it acts like seasoning in the flavour.

The mash pH. When mashing, you mix crushed malt with hot water, so that enzymes convert starch into sugar. According to John Palmer, the acidity of that mixture should be between 5.2 and 5.6 (measured at room temperature). Calcium lowers the pH, bicarbonate pushes it up. If the pH goes above about 6, more tannins dissolve from the husk and the beer can taste harsh and astringent. Dark, roasted malt is acidic by nature. That is why water with a lot of bicarbonate suits dark beer better, and water with little bicarbonate suits pale beer. Brewers sum up this balance between calcium, magnesium and bicarbonate in a single figure: the residual alkalinity.

The flavour. - Sulfate makes the hop bitterness drier and tighter. Too much makes the bitterness astringent and can smell sulfurous. - Chloride gives a fuller, rounder impression. It does not make beer maltier, but lets the malt come out better. - Sodium rounds things off in small amounts and tastes salty in large amounts. - Magnesium is food for the yeast in small amounts; too much tastes harsh and mineral. - Calcium also helps with a clear beer and the settling out of yeast.

What does not belong in it counts too. Chlorine from tap water can form chlorophenols with compounds from the wort, which taste of medicine or sticking plaster.

Soft, hard and alkaline. Soft water contains little calcium and magnesium, hard water a lot. You can boil away part of the temporary hardness (bound to bicarbonate), but not the permanent hardness. Waternet, the drinking water company of Amsterdam, gives hardness in German degrees (°dH) and mmol/l, and calls its tap water soft, at 7.8 °dH (1.40 mmol/l).

Famous brewing waters. - Pilsen: few minerals. According to the BJCP, water low in sulfate and carbonate gives Czech pilsner a strikingly soft, round hop character, despite a good deal of hops. - Burton-upon-Trent: well water with a lot of gypsum (calcium sulfate), according to Historic England ideal for pale ale. The sulfate content does differ strongly per well, though: according to water expert Martin Brungard up to 800 ppm at one brewery and around 200 ppm at another, from the same groundwater layer. - Munich: hard, lime-rich water, actually better for dark beer. For the pale Helles it had to be softened. - Dortmund: mineral-rich water, which according to the BJCP you can taste as a round, full flavour.

The 'classic' water profiles that circulate in tables are not always reliable: sources give different numbers, and Palmer himself wrote in 2025 that several profiles in his table do not produce a realistic composition.

What brewers do with water. - Remove chlorine, for example with an activated carbon filter. - Soften by boiling or, as used to be done in Munich, with milk of lime. - Add acid, such as lactic acid or acidulated malt, to neutralise the alkalinity. - Add salts: gypsum or calcium chloride. Adding gypsum is called Burtonising. - Dilute with distilled water, or reverse osmosis: that removes (almost) all the minerals, after which you build the water up again.

An English brewing book from 1846 reports that brewers disagreed about the best water: one preferred hard water, another soft. The same book attributes the quality of Burton ale to gypsum in the water. In 1830, according to that book, Burton brewers sued a publisher for libel: a book by that publisher said that they added gypsum. The gypsum turned out to be naturally present in their water, and the publisher lost.

In 1889, Alfred Barnard wrote that brewers elsewhere spent a lot of money to make their water resemble that of Burton. In 1897, the English brewery Hancock treated its water differently for each type of beer, with gypsum and other salts. In Munich, the hard water had to be softened in the 1890s for the new Helles.

A review article from 2012 states: in the past, the local water helped determine which beer styles arose in a region; thanks to water treatment, breweries became independent of it.

A tip to learn to recognise water in your glass: put a Czech and a German pilsner side by side. The Czech one has, according to the BJCP, a soft, round hop character, thanks to water low in sulfate and carbonate. In the German one, mineral-rich water can strengthen and lengthen the dry finish. In English bitters and IPAs in the Burton style, sulfate-rich water can give a dry, mineral finish, sometimes with a hint of sulfur. And with a stout: the black colour comes from roasted grain, not from the water.