Brewing water

What water actually does

The most consequential thing about brewing water is its alkalinity — principally bicarbonate — because that is what resists the acidification that happens when malt meets water. Mash pH governs enzyme activity, extraction efficiency, protein behaviour and how harshly roasted grain expresses itself. Get it wrong and the beer is thin, dull or astringent, regardless of the recipe.

Only after that do the flavour-adjacent ions matter. Sulphate tends to accentuate hop bitterness and push the finish drier; chloride tends to accentuate malt fullness and roundness. Both are tendencies in perception, not switches. Sulphate does not add bitterness — there is no bitterness in a sulphate ion — it changes how the bitterness already present is read, and at high levels it reads as harsh rather than as more.

Calcium does the practical work: it lowers mash pH, helps enzymes and proteins behave, assists yeast flocculation and improves clarity. It is the ion most brewing water is adjusted for, and it is nearly flavour-neutral.

The historical causation runs both ways

It is commonly said that a city’s water created its style — that Burton’s gypsum-rich water produced pale ale, or that Dublin’s alkaline water produced stout. The relationship is real but weaker and more contingent than that phrasing suggests. Brewers worked with the water they had and selected recipes that survived it, which is a different claim from water determining style. Once Burtonisation and modern water treatment existed, any brewery could reproduce any profile, and the causal link was severed entirely.

Each profile below carries its own caveat, because the figures are historical reconstructions of a supply that varied by source, season and century.

Historic brewing cities

• Burton-on-Trent watervery hard · strongly sulphate

  Extremely high in calcium sulphate, the water that made Burton the centre of world pale ale brewing and gave brewing the term "Burtonisation".

• Dortmund waterhard · sulphate leaning

  Hard water high in both sulphate and chloride, producing a pale lager firmer than a Helles but softer than a northern Pils.

• Dublin waterhard · sulphate leaning

  Hard and strongly alkaline, with very high bicarbonate — well matched to the acidity of heavily roasted grain.

• Edinburgh waterhard · sulphate leaning

  Hard, well-mineralised water from the city’s brewing wells, associated with Scotland’s malt-forward ale tradition.

• London watermoderately hard · balanced

  Moderately hard with substantial bicarbonate and low sulphate — suited to porter and brown beer rather than pale ale.

• Munich watermoderately hard · balanced

  Moderately hard and notably alkaline, with high bicarbonate that historically favoured darker malt over pale.

• Pilsen watervery soft · balanced

  Among the softest brewing water in the world, with almost no mineral content — the reason a heavily-hopped pale lager tastes rounded rather than harsh.

• Vienna waterhard · sulphate leaning

  Hard, moderately alkaline alpine water that suited the amber malt-forward lager Anton Dreher developed in 1841.

Reference profiles

• Balanced reference profilemoderately hard

  A neutral modern reference profile with moderate calcium and an even chloride to sulphate balance, used as a comparison baseline.