Coffee is 98% water. If your water tastes bad, your coffee will taste bad. No amount of expensive machinery or premium beans can fix that. Hardness & Alkalinity Magnesium in water helps extract fruity flavors. Bicarbonates buffer acidity. Too much hardness, and the coffee tastes chalky and flat. Too soft (RO water), and it tastes sour and empty. The Fix Use filtered tap water or bottled spring water. Avoid distilled water—it lacks the minerals needed to attach to flavor compounds.