Have you ever found yourself in a situation where, no matter how hard you try, your espresso or pour-over just doesn't taste delicious? You've tried everything: buying premium beans, grinding finer, upgrading your tamper, or using WDT tools and puck screens. If the flavor is still "off," the culprit might be the one thing you haven't changed: the water.
Why It Matters
Coffee is mostly water. In a standard pour-over, water makes up more than 98% of your cup, and even for a concentrated espresso, it accounts for 88–92%. Because water acts as the solvent that dissolves soluble compounds from your beans, its chemical makeup dictates exactly what ends up in your mouth.
While tap water in cities like Sofia is generally considered good, it still benefits from filtration to remove chlorine and other impurities that can mask the coffee's flavor. However, if you are looking for the perfect brew, you need to look closer at TDS and pH levels.
How They Interact
It isn't just about the individual numbers; it's about how TDS and pH work together during the brewing process:
• High TDS with high alkalinity: This combination acts as a buffer that neutralizes the natural fruity acids in coffee, often resulting in a cup that tastes flat, chalky, or bitter.
• Low TDS with low pH: This lacks the minerals required to extract pleasant, sweet notes, leaving your brew tasting thin, overly sour, and sharp.
Understanding the Chemistry: TDS vs. pH
While both impact your coffee, they measure completely different characteristics:
| Feature |
Total Dissolved Solids (TDS) |
pH Level |
| What it measures |
The total concentration of all inorganic and organic substances dissolved in the water. |
The concentration of hydrogen ions (H⁺) in the water. |
| Scale |
Measured in parts per million (ppm) or milligrams per liter (mg/L). |
Measured on a logarithmic scale from 0 to 14. |
| Role in Coffee |
Determines extraction power. Minerals like magnesium (Mg²⁺) and calcium (Ca²⁺) pull flavor compounds out of the grounds. |
Determines perceived flavor balance. It buffers or amplifies the natural acidity and brightness of the coffee. |
| Ideal Target |
75 to 250 ppm (150 ppm is the SCA optimal standard). |
6.5 to 7.5 (near neutral). |
⚠️ The TDS Trap
Just because your TDS meter reads 150 ppm doesn't mean it's perfect. TDS tells you how much stuff is in your water — but not what that stuff is. The SCA looks for a balance of Total Hardness (the calcium and magnesium that extract flavor) and Alkalinity (the buffer, ideally around 40 mg/L as CaCO₃, that keeps your coffee from tasting too sour or too flat). Two waters can share the same TDS reading and taste completely different in the cup.
Going Deeper: It's Not Just "How Much," But "What Kind"
While TDS tells you the total amount of minerals, the composition of those minerals changes the flavor profile:
• Magnesium (Mg²⁺) vs. Calcium (Ca²⁺): Magnesium is the "flavor extractor" that pulls out fruity, acidic notes, while Calcium primarily adds "body" and a creamy mouthfeel.
• Alkalinity: This is the water's "buffer" — and a separately measured SCA parameter (target: ~40 mg/L as CaCO₃). If it's too high, it neutralizes the coffee's natural acidity, making it taste flat or chalky.
• Chlorine: This is the biggest enemy. Even tiny amounts can create a "swimming pool" or chemical aftertaste, which is why filtration is non-negotiable.
• Sodium (Na⁺): In small doses (around 10 mg/L), it can round out sweetness, but too much will make your brew taste salty. Note: this figure comes from specialty community practice and DIY mineral recipes — sodium is not part of the official SCA Water Standard parameters.
The Bottom Line
If you're using bottled water or a DIY mineral solution, aim for that "sweet spot" of 150 ppm and a neutral pH of 7.0. You might just find that the "expensive" tasting coffee you've been chasing was hidden in your water all along.
Bonus: The Final Water Variable
Even if your mineral balance is dialled in perfectly, there's one last variable that can make or break extraction: temperature. The SCA standard calls for brewing water to hit the coffee at 92°C to 96°C (197°F–205°F). Too cool and the water won't dissolve enough of the good compounds, leaving you with a weak, under-extracted cup. Too hot and you risk scorching the grounds and amplifying bitter notes. Get the minerals right, then make sure your water is in that temperature window — and you've covered every variable the SCA cares about.
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