Geimori / Coffee Journal
Your coffee is mostly water. Its mineral composition affects taste, and scale risk matters just as much for your machine.
Start with clean, pleasant-tasting water
If your tap water smells strongly of chlorine or tastes unpleasant on its own, those qualities may carry into the cup. A suitable carbon filter can often help with chlorine and some unwanted tastes. It does not automatically remove every dissolved mineral or solve every hard-water problem.
Do not assume that distilled water or the highest-mineral spring water is the best default for brewing. Espresso machines can have specific water chemistry requirements; always check your manual.
Hardness, alkalinity and TDS are not interchangeable
| Measurement | What it tells you | Why it matters |
|---|---|---|
| Hardness | Mainly calcium and magnesium ions | Changes extraction behavior and contributes to scale formation. |
| Alkalinity | Water’s capacity to buffer acids, often associated with bicarbonate | Can soften perceived brightness; too much can flatten a lively coffee. |
| TDS meter reading | An estimate of overall dissolved ions | Does not identify which minerals are present or prove that water is safe for a machine. |
| Chlorine and off-odors | Whether water has noticeable residual treatment character | Can negatively affect flavor. |
A simple way to test brewing water
- Taste the water at room temperature and note any off-flavors.
- Look up a local water report or test hardness and alkalinity with suitable strips or a liquid test.
- If water is very hard, consider a manufacturer-approved filter or treatment method.
- Brew the same coffee with your usual and filtered water while holding grind, dose and temperature steady.
Why scale is not merely a flavor issue
Calcium carbonate scale can accumulate when hard water is heated. It may reduce flow or efficiency and can damage components over time. Filtration and water treatment should therefore be selected for both the cup and your machine’s specifications.
The Specialty Coffee Association has published water guidance for brewing, but quoted target numbers vary by document and date. Treat any chart as a useful reference, not a universal espresso-machine warranty recommendation.
The best first adjustment
Change only the water source at first. If acidity, sweetness and body shift, log the difference before adjusting grind. Tinkering with multiple variables at once makes it difficult to know what helped.
