Water treatment for pale lager and pilsner

Pale beers need soft water with near-zero alkalinity: target profiles for Bohemian and German Pilsner, salt additions for 20 L of RO water and how to bring pH to 5.2–5.4.

22 Sept 2026 · 6 min read

Pilsner malt is so pale it has almost no acidity to pull mash pH down. With bicarbonate-rich water the pH sits above 5.6 — the beer turns astringent, coarsely bitter, darker and less clear. That's why pale lagers and pilsners need very soft water with near-zero alkalinity.

Target water profile

Ion	Bohemian Pilsner	German Pilsner / Helles
Ca²⁺	10–30 ppm	30–50 ppm
SO₄²⁻	10–30 ppm	40–80 ppm
Cl⁻	10–30 ppm	20–50 ppm
HCO₃⁻	0–15 ppm	0–20 ppm

Steps for a 20 L batch

Start from 100% RO water (TDS < 10 ppm) — bicarbonate close to zero.
German Pilsner / Helles: add 1.5 g gypsum + 1.0 g CaCl₂·2H₂O per 20 L → about Ca 31, SO₄ 42, Cl 24 ppm.
Bohemian Pilsner: just 0.5 g gypsum + 0.5 g CaCl₂·2H₂O per 20 L → about Ca 13, SO₄ 14, Cl 12 ppm — very soft, like Plzeň water.
Bring mash pH to 5.2–5.4: with RO water and Pilsner malt it usually starts around 5.6–5.8. Use 2–3% acidulated malt (each 1% ≈ −0.1 pH) or 75% phosphoric acid — flavour-neutral and clean. Estimate with software, add a little at a time and re-measure.

A Castle Malting lager schedule

Castle Malting's 100 L American Lager uses mash pH 5.3 and 3 L/kg: mash in at 52°C for 5 minutes → 63°C for 40 → 72°C for 15 → mash-out at 78°C, sparge with 78°C water. W-34/70 lager yeast ferments at 10°C for two days, then 14°C to finish (about 7 days), drops to 8°C to harvest yeast and lagers at 2°C for 7 days. The beer lands at 5% ABV, 7 EBC, 20 IBU.

Lager fermentation needs a steady 10–14°C for two weeks — in Vietnam, a jacketed fermenter on a chiller is the surest route to a clean pilsner.