Introduction:To consistently extract coffee with captivating flavors, water quality is an indispensable key factor. This article delves into how the TDS value, hardness, and pH level of water affect the final flavor when brewing pour over coffee, and explores the roles of calcium and magnesium ions in the extraction process. Meanwhile, it analyzes the suitability and considerations of various types of water—from tap water, filtered water, purified water to different kinds of mineral water—to help you choose the most appropriate water source and elevate your coffee quality.
In the process of making pour over coffee, besides the quality of coffee beans and grind size, the choice of water is equally crucial. Water is not just an extraction medium; its chemical composition directly affects the release of coffee acidity, sweetness, and aroma. Therefore, understanding the TDS value, hardness, and pH level of water is essential knowledge for every coffee enthusiast.
First, let’s talk about water “hardness.” Hardness refers to the concentration of mineral ions such as calcium and magnesium in water. Though these cations are invisible to the naked eye, they can significantly alter the extraction performance of coffee. Natural water may appear clean, but it often contains metal ions such as calcium, magnesium, potassium, and sodium, as well as anions like bicarbonate, all of which together determine whether the water is “soft” or “hard.”
According to recommendations by the Specialty Coffee Association of America (SCAA), water suitable for pour over coffee should have a total dissolved solids (TDS) level between 75 and 250 ppm . However, many baristas find that when TDS is controlled below 100 ppm , it is easier to extract a balanced and layered coffee flavor. It’s important to note that TDS only reflects the total amount of dissolved substances in water, not the specific components, so this figure alone cannot determine water quality.
Among the various ions, calcium and magnesium have the most noticeable impact on coffee extraction. An appropriate amount of calcium ions helps enhance the clarity of acidity, but if their concentration is too high, it can lead to scale buildup, affecting equipment longevity and extraction stability. In contrast, magnesium ions are believed to bring out the sweetness and aroma of coffee—even at low levels, they can significantly improve overall flavor performance. Therefore, water with a well-balanced calcium-to-magnesium ratio is the ideal choice for pour over coffee.
Beyond hardness, the pH level (acidity or alkalinity) of water is another important parameter affecting coffee taste. A pH value of 7 is neutral, below 7 is acidic, and above 7 is alkaline. Generally speaking, coffee itself has a pH value of around 5 to 6, making it a weakly acidic beverage. To complement the inherent characteristics of coffee, it is recommended to maintain the pH of brewing water between 6.5 and 7 , as this range can bring out a more harmonious and smooth taste.
With the basic principles outlined above, let’s examine several types of commonly used water in daily life and assess their suitability for pour over coffee:
Tap water is the first choice for most households, but its TDS value is generally on the higher side. In some regions, noticeable limescale may even be observed at the bottom of kettles, indicating a rich content of calcium and magnesium. Additionally, tap water is often disinfected with trace amounts of chlorine, which can introduce a pool-like off-flavor, further interfering with the original flavor of the coffee. Even if the TDS value seems appropriate, it is advisable to rely on actual brewing tests and pay attention to any residual off-odors or impurities.
Filtered water can remove some impurities, but not all filters can effectively adjust TDS or the ratio of minerals. It is recommended to always check the TDS value after filtration and compare the taste differences through actual brewing. If the filtered water remains hard or still carries an odor, it is not suitable for crafting refined pour over coffee.
Purified water , having undergone high-level filtration, contains almost no minerals. While it is clean and free of impurities, it lacks elements such as calcium and magnesium that positively contribute to flavor. Coffee brewed with pure water often ends up with weak aroma, insufficient sweetness, and acidity that may seem overly sharp or unbalanced—often described as “hollow” or “flat” in overall taste.
Mineral water , due to its natural mineral content, is often mistakenly considered the best choice for brewing coffee. However, the TDS values and mineral compositions of different brands of mineral water vary greatly. For instance, some well-known brands have TDS levels as high as 489 ppm, far exceeding the standards recommended by SCAA. Using such water for brewing may lead to over-extraction or excessively intense flavors. Therefore, when choosing mineral water, be sure to check the TDS value and detailed mineral composition listed on the bottle, rather than relying solely on brand reputation or price.
Based on the above analysis, if you’re looking to select a type of water suitable for daily pour over coffee, it is recommended to opt for water with TDS below 100 ppm, a pH value close to neutral (6.5–7), and a moderate calcium-to-magnesium ratio. Such water not only clearly highlights the layers and aromas of coffee, but also aids in stable extraction performance, helping you achieve results closer to the ideal flavor with each brew.
The above content is compiled by CoffeeHunters, a coffee news website.
