Brewing Water Basics
What the minerals in your water actually do, how to tune the sulfate-to-chloride balance for a style, and how to hit mash pH. Worked from a soft Wellington water profile.
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Water is the ingredient that is easiest to ignore and surprisingly powerful once you understand it. The minerals dissolved in it shape mash enzyme activity, how hop bitterness comes across, how full the malt tastes, and yeast health. You do not need a chemistry degree — you need a few ions, one ratio, and a target pH.
This guide is worked from Wellington’s soft tap water. The principles are universal; the specific salt amounts assume a soft, low-mineral starting point. (Auckland and other supplies differ — start from your own water report.)
Start by removing chlorine
Tap water is treated with chlorine or chloramine. Both react with malt to produce a plaster / band-aid off-flavour (chlorophenols). Neutralise them first: add campden (metabisulphite) at about ½ a crushed tablet per 50 L to all brewing water, stir, and wait a couple of minutes. This step matters more than any mineral addition.
What each ion does
| Ion | Effect | Typical target |
|---|---|---|
| Calcium (Ca²⁺) | Mash enzyme health, yeast flocculation, clarity | 50 ppm minimum; 75–150 ppm typical |
| Sulfate (SO₄²⁻) | Accentuates hop bitterness — dry, crisp finish | 100–200 ppm for hoppy styles; low for malty/Belgian |
| Chloride (Cl⁻) | Accentuates malt — fullness, sweetness, roundness | 50–150 ppm for malty/hazy; low for dry/bitter |
| Magnesium (Mg²⁺) | Minor yeast nutrient | Keep below ~30 ppm (harsh above) |
| Sodium (Na⁺) | Rounds out malt at low levels | <100 ppm |
| Bicarbonate (HCO₃⁻) | Raises mash pH; buffers dark grain acidity | Low for pale beers; high only for dark/roasty |
The one lever that matters most: sulfate-to-chloride ratio
You can get a long way by thinking in terms of the SO₄ : Cl ratio, which tilts the beer’s balance:
- ~2–3 : 1 (sulfate-forward) → crisp, dry, bitter. West Coast IPA, pale ale.
- ~1 : 1 → balanced.
- ~1 : 2 (chloride-forward) → soft, round, full. Hazy IPA, malty styles.
A soft starting point: Wellington
Wellington municipal water is soft and low in minerals — close to a Pilsen profile (roughly Ca 18, Mg 4, Na 10, SO₄ 3, Cl 10, HCO₃ 60 ppm). That is a clean slate: the main job is raising calcium and setting the sulfate:chloride balance for the style. Soft water like this needs additions for hoppy beers but barely any for a delicate lager.
The common salts
| Salt | Raises | Use |
|---|---|---|
| Gypsum (CaSO₄) | Calcium + sulfate | Hop-forward bitterness, dry finish |
| Calcium chloride (CaCl₂) | Calcium + chloride | Malt body, roundness |
| Epsom salt (MgSO₄) | Magnesium + sulfate | Small yeast-health top-up (sparingly) |
| Lactic acid (88%) | — (lowers pH) | Mash pH correction, no flavour ions |
| Table salt (NaCl) | Sodium + chloride | Perceived sweetness at low doses |
Worked targets (per 23 L, from soft water)
- West Coast IPA / Pale Ale — accentuate bitterness, dry finish: ~CaSO₄ 6 g + CaCl₂ 2 g + MgSO₄ 2 g (≈ 2.5–3 : 1 sulfate:chloride).
- Hazy / NEIPA — soft and juicy: ~CaCl₂ 4 g + CaSO₄ 2 g (chloride-forward).
- Belgian / Saison — neutral base, let the yeast lead: ~CaSO₄ 3 g + CaCl₂ 2 g. On soft water, minimal additions.
- Lager / Pilsner — very soft, low sulfate: ~CaCl₂ 1–2 g, or nothing at all.
Dial these in with a calculator (Brewfather, Bru’n Water) against your own water report — these are starting points, not gospel.
Mash pH — the payoff
Mash enzymes work best in a tight pH band. Aim for:
- 5.2–5.4 for pale and hoppy ales
- 5.3–5.5 for malty and Belgian beers
- 5.4–5.6 for dark, roasty beers (the roast malt drops pH on its own)
How to do it: add your salts to the strike water before heating. Five to ten minutes after mashing in (once temperature is stable), read the mash with a calibrated pH meter. If a pale beer reads above ~5.5, add lactic acid 1 mL at a time, stir, wait 5 minutes, and re-check. On soft Wellington water with a pale grist, 1–2 mL usually does it. Adjust early — corrections after the 30-minute mark do little.
Keep sparge water around pH 5.4–5.6 too: sparging hot (75–78 °C) at high pH risks pulling tannins (astringency) out of the husks.
Quick checklist
- Campden added to all water (chlorine/chloramine gone)
- Salts weighed on a 0.1 g scale (don’t guess)
- Salts split appropriately between mash and sparge
- Mash pH checked at 5–10 min, corrected with lactic acid if high
- pH meter calibrated with fresh buffer, probe stored in storage solution
Common issues
- Mash pH too high (pale beer) — salts alone weren’t enough buffer; add lactic acid in 1 mL steps.
- Harsh, astringent bitterness — too much sulfate (>250 ppm) or tannin from a hot, high-pH sparge; cut the gypsum and treat the sparge water.
- Thin, flat finish — not enough chloride; add 1–2 g CaCl₂.
- Plaster / band-aid flavour — chlorine/chloramine not neutralised; campden next time.