Total Dissolved Solids (TDS): The sum of all substances that are soluble in water and less than 2 microns in diameter. Units are parts per million (ppm) or milligrams per liter (mg/L).
pH (pH): A way of expressing acidity, meaning the concentration of hydrogen ions; pH 7.0 is a neutral standard.
Acid: A solution with a pH lower than 7.0.
Alkaline: A solution with a pH higher than 7.0.
Hardness: A way of expressing the amount of soluble calcium and magnesium ions (positive ions). The unit is mg/liter.
Alkalinity: The ability of a solution to be neutralized by acid and prevent itself from becoming more acidic. The unit is mg/liter.
Alkaline, Alkalinity and Hardness
Alkali and alkalinity are defined differently and people are often confused. The so-called "base" generally refers to a solution with a pH value higher than 7.0. "Alkalinity" refers to the ability of a solution to prevent itself from becoming more acidic when an acid is added. Alkalinity and "hardness" are also often confusing. I only use this word when calcium and magnesium ions create hardness. This hardness is also known as "temporary hardness" because when hard water is heated, calcium and magnesium precipitate, reducing the hardness of the water. Alkalinity is produced by carbanions and carbonate ions; alkalinity is sometimes referred to as "normal hardness".
Ideal Water for Brewing
To brew a cup of coffee full of flavor and balance, refer to the recommended values in the table.
|Scope of recommendations||Impact on coffee|
|Total Dissolved Solids (TDS)||120～130ppm (mg/L)||Too low: rough flavor, lack of taste|
Too high: bland, mixed flavor
|pH (pH)||7.0||Too low: too bright and too acidic |
Too high: tastes bland
|Hardness||70～80mg/L||Too low: shallow, lack of layering|
Too high: tastes like chalk
|Alkalinity||50mg/L||Too low: bright and high acidity|
Too high: boring and dull