The SCA Water Standard
The Specialty Coffee Association (SCA) — and before it the SCAA — publishes a recommended water profile for brewing, the closest thing the industry has to an agreed definition of "good water." It exists because water is the great hidden variable (see Why Water Matters), and a shared target lets roasters, cafés, and competitors compare results on common ground. The standard is best understood as a target box with an acceptable range and an "ideal" centre point, not a single magic recipe.
#The Numbers 🎯
| Attribute | Target / ideal | Acceptable range |
|---|---|---|
| Total Dissolved Solids | ~150 ppm | 75–250 ppm |
| Calcium hardness (GH) | ~68 ppm (as CaCO₃) | 17–85 ppm |
| Total alkalinity (KH) | ~40 ppm (as CaCO₃) | at/near 40 ppm |
| pH | 7.0 (neutral) | 6.5–7.5 |
| Sodium (Na⁺) | ~10 mg/L | low |
| Odor | clean / odor-free | — |
| Chlorine | 0 | 0 |
Those map directly onto the TDS and GH/KH ideas: moderate total minerals, hardness comfortably above alkalinity, neutral pH, and no chlorine (which causes off-flavors and is the first thing a filter should remove).
#How to Read It
The famous "68/40" pairing — ~68 ppm calcium hardness and ~40 ppm alkalinity — is the ideal centre, while the wider TDS band of 75–250 ppm marks where water is still considered acceptable. The intent is a water that extracts efficiently (enough GH) without over-buffering acidity (modest KH), stays kind to equipment, and adds no flavors of its own. Many build-your-own-water recipes are explicitly engineered to land on or near this profile.
#Limits and Criticisms ⚠️
The standard is a useful launchpad, but it is not gospel, and serious brewers treat it with nuance.
- The acceptable range is very wide. A 75 ppm water and a 250 ppm water both "pass" yet brew dramatically different cups, so passing the standard does not guarantee a great result.
- It specifies total hardness, not the magnesium-to-calcium ratio — yet that ratio strongly shapes flavor (magnesium for brightness, calcium for body). Two compliant waters can taste very different.
- It targets a general optimum, not your coffee. A juicy washed Ethiopian and a dark espresso blend do not want identical water; the ideal shifts with roast and bean.
- Measurement is fuzzy — cheap TDS pens read conductivity, not composition, so "150 ppm" on a pen tells you little about GH/KH balance.
The honest takeaway: hit the SCA box to rule water out as a problem, then use taste — your developing palate — to fine-tune within it. When dialing a new coffee, the standard tells you your water is sane; grind and technique do the rest.
#Continue Reading
- Building Water — Recipes and Remineralization — recipes engineered to hit this profile
- Water Chemistry — Hardness and Alkalinity — the GH/KH detail the standard summarizes
- TDS and Mineral Content — what the ~150 ppm headline figure means
- Filtered, Bottled, and Tap Water — does your everyday water fit the box?
- Water for Coffee — back to the water hub