Specialty coffee nerds love to talk about TDS, magnesium, and bicarbonate. At home, you mostly need a simple idea: water should taste good on its own and shouldn’t fight your coffee. If your tap is chlorinated, metallic, or smells like a pool, it will show up in the cup. A decent charcoal filter or bottled water with moderate mineral content (not distilled, not ultra-hard) is usually enough to get out of your own way.
What extraction actually means
Extraction is how much of the coffee’s soluble mass ends up in your beverage. Under-extraction often tastes sour, sharp, or a little “empty.” Over-extraction often tastes bitter, harsh, or drying. Sweetness and clarity usually live between those poles — and your grinder is the coarse/fine dial, while water temperature and contact time are the clock.
Temperature (without thermometer anxiety)
For most manual brewing, water off boil that’s rested 30–60 seconds lands in a friendly range for light to medium roasts. Very dark roasts can be a little gentler — hotter water can spotlight ashiness. If you don’t have a kettle with degree control, don’t stress: consistency matters more than chasing a single magic number.
Ratio: strength vs extraction
Brew ratio (coffee to water by weight) mostly sets strength — how concentrated the drink is. A 1:15 cup is “beefier” than a 1:17 cup if extraction is similar. Extraction is about how thoroughly you pull from the grounds; you can have a strong cup that’s weak on flavor (under-extracted) or a milder cup that’s balanced (well-extracted).
Start around 1:16 if you want a middle path, then move ratio after grind is roughly right. Changing ratio and grind at the same time makes troubleshooting fuzzy — adjust one variable, taste, then the next.
Hard water and descaling (short version)
Scale buildup in kettles and espresso machines is real chemistry, not a conspiracy. If your water is very hard, you’ll taste it less in one pourover than in a machine with tiny tubes — but long term, filtering helps equipment too. Follow your gear manufacturer’s guidance; we’re not your warranty department.
What to read next
Put water together with motion through the bed in Brew methods, and pair it with grind adjustments from Grinding.