Your Water Is 98% of the Cup — Here's How to Fix It

If your coffee tastes flat no matter what you change, check the water before you blame the beans — it's 98% of the cup.

The problem

Very hard water mutes acidity and clarity; ours in Vilnius reads around 320 ppm, hard enough to flatten any roast. Very soft or distilled water swings the other way: sour, hollow cups and eventually corroded kettles.

The range brewing wants

Roughly 50–150 ppm total hardness with some buffering — enough minerals to extract flavour, not enough to smother it. Most EU tap water sits well outside this.

The fixes, cheapest first

Bottled water with a mineral content in range (check the label). A coffee-specific filter jug that targets the brewing range rather than just chlorine. Or remineralising drops in distilled water if you want full control.

Test it yourself: brew the same coffee with your tap water and with in-range water, side by side. It's the most convincing €2 experiment in coffee.