Can I use tap water for brewing coffee?

Water constitutes roughly 98% of a brewed cup of coffee, yet it is frequently the most overlooked variable in the supply chain. While producers invest immense labor into soil health, fermentation, and drying to create specific flavor profiles, the final extraction is entirely dependent on the solvent—your water. Tap water is rarely consistent; it is a product of local geology and municipal treatment, meaning it can fluctuate seasonally. The primary mechanism at play is buffering capacity. If your water has high alkalinity (bicarbonates), it neutralizes the organic acids in the coffee, resulting in a flat, muddy, or 'chalky' cup that obscures the producer's work. Conversely, water that is too soft may lead to over-extraction, creating harsh, bitter notes. A common misconception is that all filtration is equal. Standard carbon pitchers effectively remove chlorine—which can impart a medicinal, chemical taste—but they do not adjust mineral hardness or alkalinity. To truly honor the producer's effort, one must understand their local water profile. If your tap water is excessively hard, ion-exchange filtration is necessary to bring mineral levels within the Specialty Coffee Association (SCA) target range of 50–175 ppm total hardness. Ultimately, if your water tastes unpleasant on its own, it will inevitably degrade the quality of the coffee, regardless of the bean's origin or roast quality.