Optimal Water Mineralization for Specialty Coffee
Calculate water hardness and mineralization for specialty coffee. SCA standards: TDS 75-250 ppm, hardness 50-175 mg/L, pH 6.5-7.5. Optimize your brewing.
- Data verified · June 2026
- Edited by Martín Rodríguez
- Formula verified by automated tests
- Private — runs on your device
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How to use this calculator
Follow this tool’s steps, then review its formula, assumptions, and limits below.
When to use this calculator
- Your coffee tastes flat or metallic—you suspect the water.
- You're buying bottled water and want to know which brand works.
- You have a water filter and want to optimize it.
- You make specialty coffee and want to compete on quality.
- Your espresso channeling looks off and you suspect mineralization issues.
SCA water standard for brewed coffee
The Specialty Coffee Association's recommended water composition. "Target" is the bullseye; "acceptable range" is the window within which water still brews well.
| Parameter | Target | Acceptable range |
|---|---|---|
| TDS (total dissolved solids) | 150 ppm | 75–250 ppm |
| Total hardness | ~68 mg/L CaCO₃ | 50–175 mg/L |
| Calcium hardness | 51 mg/L CaCO₃ | 17–85 mg/L |
| Alkalinity (bicarbonate) | 40 mg/L CaCO₃ | 40–75 mg/L |
| pH | 7.0 | 6.5–7.5 |
| Chlorine | 0 mg/L | 0 mg/L |
| Sodium | 10 mg/L | ≤ 30 mg/L |
Source: Specialty Coffee Association water quality standard. Hardness and alkalinity are both expressed as CaCO₃ equivalent, which is why a TDS meter alone can't confirm SCA compliance — it doesn't separate hardness from alkalinity.
Common bottled & tap waters for coffee
Approximate published TDS and pH for widely available waters, scored against the SCA window. Brand figures vary by source spring and batch — treat as a starting guide, not a spec.
| Water | TDS (ppm) | pH | Good for coffee? |
|---|---|---|---|
| Volvic | ~130 | 7.0 | ✓ Excellent — sits near the target |
| Villa del Sur | ~85 | 7.1 | ✓ Good — on the soft side |
| Villavicencio | ~240 | 7.5 | ✓ Usable — near the high edge |
| Buenos Aires tap | ~150–200 | 7.0–7.5 | ✓ If carbon-filtered for chlorine |
| Evian | ~357 | 7.2 | ✗ Over-mineralised — dull, over-extracted |
| Softened (salt) water | varies | 7–8 | ✗ Sodium replaces hardness — flat, salty |
| Distilled / RO (unmineralised) | 0 | ~5.5 | ✗ No minerals to extract — hollow cup |
Distilled and reverse-osmosis water need remineralising (e.g. Third Wave Water or a pinch of mineral blend) before they'll brew well. For RO systems, a remineralisation cartridge is the simplest fix.
How it works
Why Water Matters
Coffee is 98.5% water in a brewed cup, so the water you brew with does as much for the flavour as the beans. Its mineral composition extracts different compounds from the grounds at a chemical level: minerals act as polar solvents that bind selectively to different flavour molecules during extraction.
The practical takeaway: you want moderate hardness with low-to-moderate alkalinity. That's why distilled or reverse-osmosis water tastes hollow (nothing to extract with) and why heavily mineralised bottled water like Evian (~291 mg/L TDS) over-extracts into a dull, muddy cup. The SCA target sits deliberately in the middle.
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SCA Reference Window
The Specialty Coffee Association's Water Quality Standards (2018) define the following targets for brewed coffee:
| Parameter | Acceptable Range | Target |
|---|---|---|
| TDS | 75–250 mg/L | 150 mg/L |
| Total Hardness (as CaCO₃) | 50–175 mg/L | 68–85 mg/L |
| Alkalinity (as CaCO₃) | 40–70 mg/L | ~68 mg/L |
| pH | 6.5–7.5 | 7.0 |
| Sodium | <30 mg/L | 10 mg/L |
These targets were developed for filter/pour-over brewing. For espresso, many specialty roasters work with slightly softer water (hardness 50–100 mg/L as CaCO₃) to slow scale accumulation in group heads and boilers.
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How the Calculator Works
The tool takes three inputs — Mg²⁺, Ca²⁺, and HCO₃⁻ (in mg/L) — and does the following:
1. Converts individual ions to total hardness expressed as CaCO₃ equivalents, using the standard conversion factors: Mg²⁺ × 4.12 and Ca²⁺ × 2.50.
2. Converts bicarbonate to alkalinity as CaCO₃: HCO₃⁻ × 0.82.
3. Estimates TDS from the ionic concentrations using a standard approximation (actual TDS requires a conductivity meter — this is a calculated estimate).
4. Compares all values against the SCA window and flags which parameters are out of range and in which direction.
> Important: the calculator works with the three most flavour-relevant ions. It does not measure chlorine/chloramine, silica, iron, or other contaminants that also affect taste and equipment. If your tap water smells of chlorine or has known iron issues, address those separately before optimising minerals.
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How to Read Your Numbers
Two common failure modes:
A less obvious failure mode: low hardness + high alkalinity. This is common with some municipal water supplies. You have little extraction power but the alkalinity still suppresses acid — the result is a flat, low-complexity cup with no brightness at all. The fix here requires both increasing mineral content and reducing alkalinity, usually via partial RO filtration followed by remineralisation.
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What This Calculator Does NOT Cover
Example: Buenos Aires Tap Water
Frequently asked questions
Is distilled water bad for coffee?
Can you use tap water for specialty coffee?
Is a Brita filter enough for specialty coffee?
Does Third Wave Water work for specialty coffee?
Does hot brewing water affect mineral composition?
Is it worth optimizing water for regular coffee?
What's the best water pH for brewing coffee?
How do I know if my water is too hard or too soft?
Sources & references
Methodology & trust
Cooking calculator with its formula verified automatically against Specialty Coffee Association (SCA), per our editorial policy and methodology.
Updated: June 2026. Parameters are verified periodically against the cited sources.
Calculations run 100% in your browser. We do not store or transmit your data.
Indicative results. For critical decisions, consult a professional.
Rodríguez, M. (2026). Optimal Water Mineralization for Specialty Coffee. Hacé Cuentas. https://hacecuentas.com/en/water-mineralization-coffee
Content licensed under CC-BY 4.0 — reuse it citing the source with a link to Hacé Cuentas.