Journal//2 min read
What the SCA Water Chart actually says
The Specialty Coffee Association does not publish a water standard. It publishes the Water Quality Handbook (2018) and the Water Chart. The chart's target zone sits at roughly 50–110 ppm CaCO₃ total hardness and 40–65 ppm CaCO₃ alkalinity — about 2.8–6.2 °dH and 2.2–3.6 °dH respectively.
Search for water and coffee and you will be told, confidently and repeatedly, what “the SCA standard” requires. It is worth saying plainly: no such standard exists. The SCA's own published-standards register lists standards for cupping, water-free green grading, roast colour and brewing equipment. There is no water standard on it, and none listed as in development.
What does exist
- The SCA Water Quality Handbook (Wellinger, Smrke & Yeretzian, 2018) — a book, sold by the SCA.
- The SCA Water Chart — a one-page graphic plotting alkalinity against total hardness, with taste outcomes at the corners.
The numbers still circulating from the older 2009 SCAA document — 150 ppm TDS, alkalinity “at or near 40 mg/L” — belong to a superseded text, not to current guidance.
The target zone, in the units your utility uses
Both axes of the chart are in ppm CaCO₃. Converting at 1 °dH = 17.85 ppm CaCO₃ and 1 °f = 10 ppm CaCO₃:
- Total hardness — 50 to 110 ppm CaCO₃, that is 2.8 to 6.2 °dH, or 5.0 to 11.0 °f.
- Alkalinity — 40 to 65 ppm CaCO₃, that is 2.2 to 3.6 °dH, or 4.0 to 6.5 °f.
The four corners, which are the useful part
The chart labels the extremes, and the labels are what make it worth reading. High hardness with low alkalinity: heavy, dull, sour. High hardness with high alkalinity: heavy, chalky, flat. Low hardness with low alkalinity: weak, sour, sharp. Low hardness with high alkalinity: weak, chalky, flat.
Weight runs with hardness. The acid axis runs with alkalinity. Neither corner label mixes the two.
That is the entire argument for measuring both numbers rather than one. It also explains why a city average is a starting point rather than an answer: most European utilities publish both figures, and they are worth looking up for your own address.
Questions this raises
- Is there an SCA standard for brewing water?
- No. The SCA's published-standards register contains no water standard. Water guidance appears in the SCA Water Quality Handbook (2018) and the SCA Water Chart, which are a book and a chart rather than a normative standard.
- What is the SCA Water Chart target zone?
- Approximately 50–110 ppm CaCO₃ total hardness and 40–65 ppm CaCO₃ alkalinity, which is roughly 2.8–6.2 °dH hardness and 2.2–3.6 °dH alkalinity.