Water Quality and Coffee: Why Your Tap Water Is Holding Back Every Cup You Brew

By PURE EARTH COFFEE  ·  May 23, 2026  ·  Brew Better

What Water Actually Does During Extraction

Water extracts flavor compounds from coffee through a process driven by the concentration gradient between the water and the coffee grounds. The minerals dissolved in water — primarily magnesium and calcium — play a specific and critical role in this extraction. Magnesium ions bind selectively to the aromatic flavor compounds in coffee, including the fruity esters and floral aldehydes that define specialty coffee's most prized characteristics. Coffee brewed with magnesium-rich water extracts these aromatic compounds more efficiently than coffee brewed with low-mineral water. Calcium contributes differently — calcium ions bind to the bitter chlorogenic acid compounds in coffee and effectively mute some of the bitterness that would otherwise extract. The result is that water with an appropriate balance of magnesium and calcium produces a sweeter, more aromatic, less bitter cup than either distilled water (which under-extracts and tastes flat) or heavily mineralized water (which over-extracts and produces chalky, harsh flavors).

The SCA Water Quality Standard

The Specialty Coffee Association publishes a water quality standard for brewing that represents the scientific consensus on optimal extraction parameters: Total Dissolved Solids (TDS) of 150ppm (range: 75-250ppm), calcium hardness of 50-175ppm (ideally around 68ppm), pH of 7.0 (range: 6.5-7.5), no chlorine or chloramine detectable. Most municipal tap water falls outside these parameters in at least one dimension. Hard water areas (above 300ppm TDS) over-extract and produce chalky, muted flavor. Very soft water areas (below 50ppm TDS) under-extract and produce thin, flat coffee. Chlorine — present in most municipal water — suppresses aroma perception and adds off-flavors that are particularly noticeable in light roast coffees whose aromatic complexity is their defining characteristic.

What to Do About It: Practical Solutions

The most practical home solution for most brewers is filtered water. A standard activated carbon pitcher filter (Brita, PUR) removes chlorine and chloramine effectively and reduces some heavy metals, but does not significantly alter mineral content. This is adequate for most municipal water that falls within acceptable TDS ranges — the chlorine removal alone produces a noticeable improvement in cup quality for light and medium roast coffees like our Ethiopian Light/Medium Roast and Kenya AA Medium Roast. For brewers in hard water areas (above 250ppm TDS), a reverse osmosis filter with a remineralizing cartridge produces water closest to the SCA standard. For the most precise water control, companies like Third Wave Water produce mineral packets that transform distilled water into a precisely calibrated brewing water. Third Wave Water's espresso profile (designed for espresso machines) and classic profile (designed for filter brewing) both target the SCA parameters and are used by competition baristas who need to control water variables precisely.

What About Espresso Machines Specifically

Water quality matters even more for espresso machines than for filter brewing because the same water that brews the espresso also circulates through the machine's internal components. Hard water deposits scale on heating elements, group heads, and internal pipes — reducing machine efficiency, increasing electricity consumption, and eventually causing component failure. Commercial espresso machine warranties from brands including Victoria Arduino and Nuova Simonelli explicitly require water filtration as a condition of warranty coverage. Our commercial equipment lineup and our wholesale team both recommend BWT Bestmax or 3M Aqua-Pure filtration for all commercial espresso installations.

You have been spending real money on great coffee and real time on your brewing technique. Your water is the variable you have not addressed yet. Fix it and every cup you make gets better immediately. -- PURE EARTH COFFEE