The water you brew with can shape the taste of your coffee as much as the coffee itself. Today, we explore the science behind it.
BY ANGEL CASTILLO
BARISTA MAGAZINE ONLINE
Featured photo courtesy of Getty Images
What to know:
- Different aspects of the water you use to brew coffee—like pH level or mineral concentration—impact how your brew tastes
- The Specialty Coffee Association recommends using water with around 150 ppm total dissolved solids (TDS), no chlorine, and a pH of 6.5-7.5
Have you ever heard that New York bagels are good because of the water used in the dough? This poses the question: Is the same true for coffee?
While water isn’t the only thing making New York bagels taste the way they do, it does play a big role in shaping their iconic flavor and texture. And the same goes for coffee—the type of water you use (and what it’s in it) can dramatically alter the taste of your brew.
Considering water makes up more than 90% of espresso and nearly 99% of brewed coffee, the quality and composition of water dramatically affect extraction, flavor clarity, mouthfeel, and balance. For baristas and home brewers alike, water can impact the taste of your coffee almost as much as the coffee itself.
A study by researchers at Universidad de La Sabana highlights the relationship between water composition and coffee extraction, reinforcing what many coffee professionals already know intuitively: Minerals in water directly influence how flavors are pulled from coffee grounds.
The conversation around water quality has increasingly entered mainstream coffee culture as well. In an article for the Delaware News Journal, writer Anitra Johnson describes water as a “main ingredient” in brewing café-quality coffee at home—a sentiment echoed across the specialty-coffee industry.
Understanding TDS and extraction
One of the key measurements in coffee water science is TDS, or total dissolved solids. TDS measures the amount of dissolved minerals and substances present in water. According to research by Andrea Dietrich and Connor Gallagher for the American Water Works Association, these dissolved minerals significantly influence both the taste of water itself and the extraction process during brewing.
Minerals such as calcium and magnesium help extract flavor compounds from coffee grounds. Their presence can influence whether a cup tastes bright, smooth, bitter, sour, or balanced. Water additives, including chlorine used in municipal water treatment, can also alter flavor.
For coffee drinkers who enjoy a straight espresso, black coffee, or cold brew, these subtle differences become especially noticeable. Even drinks with milk or sweeteners can be affected by the underlying quality of the brew water.
Hard water vs. soft water
Water is often described as either “hard” or “soft,” terms that refer to mineral concentration.
According to Premier H2O, hard water contains higher levels of calcium and magnesium. While these minerals can improve extraction and intensify flavor, excessively hard water may create bitterness and contribute to scale buildup in espresso machines and brewers.
Chlorine presents another challenge. Commonly added to tap water for sanitation, chlorine can transfer unwanted flavors into coffee. If brewing water smells strongly of chlorine, there is a good chance those chemical notes will appear in the cup as well.
At the opposite end of the spectrum, overly purified water can also create problems.
Distilled water lacks many of the minerals necessary for proper extraction, often producing coffee that tastes flat or muted. Reverse-osmosis filtration systems, while effective at removing contaminants, can sometimes strip away too many dissolved solids if minerals are not reintroduced afterward.
According to Sensorex, a water treatment sensor manufacturer based in Garden Grove, Calif., water with extremely low mineral content may produce coffee that appears lighter-bodied and less complex.
Does alkaline water improve coffee?
In recent years, you may have noticed alkaline water growing in popularity—but what role can it play in the coffee world?
Water naturally contains minerals such as calcium, magnesium, potassium, sodium, bicarbonate, and trace elements, according to research published through the National Library of Medicine. Higher bicarbonate levels contribute to alkalinity, which can affect how coffee acidity is perceived.
For some drinkers, alkaline water creates a smoother, less acidic cup. The added minerals may also help highlight certain flavor notes. However, balance remains essential. Water with excessively high alkalinity can dull acidity and contribute to over-extraction, leaving coffee tasting heavy or one-dimensional.
The SCA’s recommendation
With so many variables in play, what water does the coffee industry actually recommend?
The Specialty Coffee Association (SCA) suggests brewing with clean, odor-free water with 75–150 ppm total dissolved solids (TDS). The organization also recommends water with:
- Zero chlorine
- Calcium hardness between 50–175 ppm
- Alkalinity between 40–75 ppm
- A pH between 6.5 and 7.5
These standards aim to create balanced extraction while preserving clarity and sweetness in the cup.
Most coffee drinkers are not measuring TDS before their morning brew, but understanding the basics can still improve results. Water that smells clean, tastes balanced, and contains moderate mineral content is more likely to produce a flavorful and well-rounded cup than either heavily treated tap water or completely stripped distilled water.
Why water matters
Coffee conversations often focus on origin, roast profile, grind size, or brew method. Yet water—the ingredient present in the greatest quantity—can be just as influential.
Whether dialing in espresso or brewing a simple pourover at home, paying attention to water chemistry may be the difference between a flat cup and one with clarity, sweetness, and complexity.
ABOUT THE AUTHOR
An artist based in Los Angeles, Angel Castillo is host of a South American food pop-up, Gatitos Cocina. Their family has a history of growing coffee in Ecuador and continues an at-home practice in San Diego, California.
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