Brewing.
Weigh your coffee and water, note your grind setting and keep a record of the result. Change one thing at a time. A repeatable method makes it easier to understand what changed in the cup.
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Measure your brew.
Use a scale that reads in grams, a timer and a grinder. For filter and immersion brewing, “water” means the water added during brewing, excluding water used to rinse or preheat. For espresso, the ratio uses the weight of the espresso in the cup.
Grind.
Grind just before you brew. Change it in small steps, one brew at a time, and note each setting.
Taste and adjust.
Taste the coffee before making a change. Keep a note of the result and change one thing for your next brew.
Water shapes the cup.
Water is an ingredient in every cup. Its mineral composition and buffering capacity can change the result, even when the coffee, grind and recipe stay the same.
Minerals. Calcium and magnesium contribute to hardness and can interact with coffee compounds. More minerals do not automatically make a better cup.
Alkalinity. This is water’s ability to neutralise acids. High alkalinity can soften a coffee’s brightness; low alkalinity leaves more of its acidity perceptible. The right balance depends on the coffee and brewing method.
TDS. Total dissolved solids describe how much dissolved material the water contains. A single ppm reading does not reveal its mineral composition, hardness or alkalinity. These are different measurements.
Choose your water.
Start with fresh drinking water that tastes clean. Choose treatment for the water you actually have: some filters reduce chlorine taste while retaining minerals; others also reduce carbonate hardness. “Filtered” alone does not describe the result.
For bottled water, read the mineral analysis rather than choosing by brand or price. Calcium, magnesium and bicarbonate are useful clues. Bicarbonate in mg/L is not the same measurement as alkalinity reported as CaCO₃.
Keep the coffee, grind, dose and brew recipe fixed when comparing suitable waters. Taste the cups as they cool, and keep a note of the water you used. This gives you a clearer comparison.
Protect your equipment.
Water that tastes good in filter coffee still needs to meet your espresso machine’s specifications. Scale formation and corrosion depend on water chemistry and operating conditions.
Check hardness and alkalinity separately, and follow the manufacturer’s limits for pH, chlorides and other parameters. Chloride is different from the chlorine that can affect water’s smell or taste. Do not use untreated distilled or reverse-osmosis water in a machine unless its instructions specifically allow it.
Berlin’s tap water is generally hard. Check the Berliner Wasserbetriebe analysis for your postcode, then choose suitable treatment and maintain it as instructed. These are regional data, not a measurement at your tap.