When brewing a high-quality cup of coffee, factors such as bean degassing, roast profile, and grind size etc are essential. However, water also plays a vital role that should not be underestimated. In fact, over 90% of a cup of coffee is composed of water, meaning the quality of the water has a direct effect on the aroma, mouthfeel, and overall flavor profile of the brew.

The Relationship Between Water Minerals and Coffee Flavor

Water sources from different regions contain varying levels of minerals such as calcium (Ca), magnesium (Mg), sodium (Na), and bicarbonates (HCO₃⁻) etc. These minerals not only influence the hardness of the water but also significantly affect the coffee extraction process. For instance, appropriate levels of calcium and magnesium can help release aromatic compounds in coffee, enhancing flavor complexity. However, excessive minerals may result in bitterness or an overly heavy body.

One factor worth particular attention is the level of bicarbonates. When present in excess, bicarbonates suppress the natural acidity of coffee, leading to a flat or muted cup that lacks the distinct characteristics of the beans.

Professional Standards: Reference Values for Ideal Brewing Water

According to the Specialty Coffee Association (SCA), ideal brewing water should meet the following criteria:

Acceptable Total dissolved solids (TDS) level for water: 75-250 parts per million (ppm)

Calcium hardness: 50-175 ppm CaCO3

Alkalinity: 40-75 ppm CaCO3

pH: 6.5-7.5

Unless you’re very technically minded, these measures mean absolutely nothing. So let’s take a closer look at the elements of water that affect the taste of your brew. 

All elements except for H2O - namely, inorganic salts such as calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates, along with a minuscule amount of organic compounds—comprise the TDS of water.  The Specialty Coffee Association (SCA) has developed standard water parameters for brewing coffee. The organization has determined that an acceptable TDS level for water is 75–250 mg/L,(75-250 ppm) 

Calcium hardness is a measure of the amount of calcium and magnesium in the water. The SCA recommends using water with a calcium hardness of 50-175 ppm CaCO3. This level of minerals helps to create a balanced flavour in the coffee.

Alkalinity is a measure of the water’s ability to neutralise acids. The SCA recommends using water with an alkalinity of 40-75 ppm CaCO3. This level of alkalinity helps to buffer the acidity of the coffee and create a smoother flavour.

pH is a measure of the water’s acidity or alkalinity. The SCA recommends using water with a pH of 6.5-7.5. This is a neutral pH that will not affect the flavour of the coffee.

If you’re not sure what type of water you have at home, you can test it using a water test kit. You can also contact your local water utility to find out the mineral content and pH of your tap water. There are also several websites where you can check the water hardness in your area.

But with all that in mind, what do you do with that information? 

Here are the roles certain elements play:

• Calcium helps to extract flavour from the coffee grounds and put it into your cup.

• Magnesium helps to bind to certain flavour compounds.

• Bicarbonate helps to keep the water’s acidity and other properties balanced. If you have a balanced acidity in your water, your brew will stay true to the acidity of the coffee itself, rather than throw off the profile. 

Water within this range helps balance sweetness, acidity, and bitterness in coffee, while also showcasing the bean’s origin and roast profile.

How Different Water Sources Affect Flavor

Common water sources include tap water, bottled mineral water, filtered water, distilled water, and reverse osmosis (RO) water. Each of these sources varies in mineral content and impacts the final cup differently. For example:

• Distilled or pure RO water: Contains nearly zero minerals. While it minimizes equipment wear, it has weak extraction power and often results in a flat, underdeveloped cup.

• Hard water (high mineral content): Can cause over-extraction, masking delicate flavors and contributing bitterness.

• Filtered tap water: When managed properly, it can offer stable and balanced results, making it suitable for daily brewing of specialty coffee.

Conclusion: Water Quality Management Is an Essential Element of Specialty Coffee

For every quality-focused coffee enthusiast and professional, water is not just a medium for extraction—it is a hidden ingredient as important as the coffee beans themselves. Whether you brew with pour-over, espresso, immersion, or cold brew methods, using water of the right quality allows you to accurately express the full flavor potential of your beans.

Based on our experience, we recommend keeping the Total Dissolved Solids (TDS) in your brewing water between 50–100 ppm. This range effectively brings out the coffee’s complexity, floral and fruity acidity, sweetness, and overall balance, while maintaining a clean and crisp finish. We suggest using Reverse Osmosis (RO) water as a base, then adding mineral treatments from APAX LAB, LOTUS, AQUACODE, or Third Wave Water to adjust the mineral composition for optimal results.