How Does Bottled Water Affect Coffee Brewing?

For coffee brewing, bottled water matters because water is the largest part of black coffee and takes part in extraction. A blind tasting compared two bottled waters with a clear price gap, plus Nongfu Spring as a store-style control, using Yirgacheffe Red Cherry and Diamond Mountain. Acidity, alkalinity, softness, hardness, TDS and calcium and magnesium ions explain why the same beans taste different.

The test focused on large, friendly-priced bottled water bought through a common food delivery platform, since that is what most people reach for. Nongfu Spring served as a reference point because shops use it often. For any coffee enthusiast, the practical takeaway is that price alone does not predict a good result; mineral content and hardness shape extraction, so matching water to the beans and the brew method matters more than paying for an expensive label.

Water is the largest component of black coffee and directly participates in and influences the extraction process, so differences in water quality often bring about completely different flavor expressions. There are many types of bottled water on the market, with prices ranging widely from high to low, and whether more expensive water is more suitable for brewing coffee has become a question for many brewing enthusiasts. This article uses two types of bottled water with an obvious price difference as test subjects, and adds Nongfu Spring, commonly used in stores, as a control, conducting blind tasting comparisons with two coffees, Yirgacheffe Red Cherry and Diamond Mountain. At the same time, from the perspectives of acidity and alkalinity, softness and hardness, TDS, and calcium and magnesium ions, it explains the principles by which water quality affects extraction, helping coffee enthusiasts understand how to choose more suitable water for brewing coffee.

As the main component of coffee, water not only accounts for the vast majority of a cup of black coffee, but also influences the degree to which various substances are extracted, thereby giving flavor and mouthfeel different appearances. Therefore, understanding water's effect on coffee is basic knowledge that every enthusiast is worth mastering.

There are many brands of drinking water on the market, and their compositions, purification methods, and usage scenarios also differ. It is precisely because the actual effects differ noticeably that discussion and curiosity are continually stirred up. For example, not long ago, a brewing enthusiast asked: "Will coffee brewed with the most expensive water taste better than with cheap water?"

This question is actually difficult to have a standard answer to, because we cannot define what counts as "the most expensive water" or "the cheapest water." However, Front Street has always been willing to try things hands-on and does not want to let go of any topic worth exploring, so today, around this question, let's conduct a "playing with water" test.

Considering that in daily coffee brewing, people often prioritize bottled water with sufficient capacity and a friendly price, the focus of this article's test is also on this type of product. Front Street opened a commonly used food delivery platform and directly filtered bottled water by most expensive and cheapest to place orders, ultimately selecting Kunlun Mountain Snow Mountain Mineral Water at 19.9 yuan/5L and Dinghu Mountain Spring Drinking Natural Water at 6.9 yuan/5L. (Although Evian water, whose price attracts more attention, is more famous, its TDS value reaches 489ppm, far above the upper TDS limit for coffee water, so it is not suitable for brewing coffee, and therefore is not discussed separately here.)

During the experiment, Front Street also added Nongfu Spring, used for store production, as a control, and selected two coffees for brewing: one was Yirgacheffe Red Cherry, with outstanding fruity acidity, and the other was Diamond Mountain, leaning toward nutty notes. To avoid preconceptions, the brewed coffees were shuffled in order and tasted in a "blind tasting" manner, observing their respective flavor expressions.

First round of experiments

Coffee beans: Yirgacheffe · Sun-dried Red Cherry

Dose: 15 grams

Coffee-to-water ratio: 1:15

Water temperature: 93°C

Grind size: EK43s setting 10

Three-stage pour: 30g-90g-105g

Dinghu Mountain: Mainly flavors of lemon, grapefruit, and berries, with especially prominent acidity, a short finish, a slight wateriness, and a relatively thin aroma; (TDS: 1.27)

Nongfu Spring: Has flavors of citrus, sweet orange, and black tea, shows berry acidity at low temperature, has a soft mouthfeel, and is balanced in acidity, sweetness, and bitterness; (TDS: 1.31)

Kunlun Mountain: Thick mouthfeel, mainly flavors of caramel and orange, with a bit of strong tea character, but the bitterness is obvious and lingers persistently on the tip of the tongue. (TDS: 1.33)

Second round of experiments

Coffee beans: Hacienda La Esmeralda · Diamond Mountain

Dose: 15 grams

Coffee-to-water ratio: 1:15

Water temperature: 91°C

Grind size: EK43s setting 10

Three-stage pour: 30g-90g-105g

Kunlun Mountain: On entry there are caramel and faint chocolate aromas, the flavor is concentrated only in the front section, the mouthfeel is monotonous, and there is almost not much finish; (TDS: 1.31)

Dinghu Mountain: The flavor is mostly plum, bayberry acidity, and the sweet aroma of cocoa, with a light mouthfeel, and at low temperature the coffee is slightly sharply acidic; (TDS: 1.36)

Nongfu Spring: Nut and cocoa aromas are obvious, at low temperature there is the acidity of dark berries and stone fruits, as well as a bit of sucrose sweetness and a fermented finish of ripe fruit. (TDS: 1.32)

Judging from the coffee flavors brewed with the three types of water, the most "expensive" water did not bring better results than the most "cheap" water. The coffee brewed with Dinghu Mountain Spring Drinking Water, the lowest-priced, had more prominent acidity and lower body; the overall flavor of coffee brewed with Nongfu Spring was more balanced; while Kunlun Mountain Mineral Water, the highest-priced, was not only sharp in mouthfeel but also weakened some of the aroma, making the coffee taste lacking in layers.

Which factors in water affect coffee extraction?

As the main solvent, water carries the task of extracting various soluble flavor substances from coffee. Generally speaking, to make coffee taste good, water quality first needs to have moderate softness and hardness, and second depends on acidity and alkalinity.

The pH value of coffee is usually between 5 and 6, so it is weakly acidic. If alkaline water is used to brew coffee, it will neutralize part of the acidic substances in the coffee, reducing acidity and thereby affecting the balance of the overall taste. Brewing water with a pH value of 6.5 to 7 is generally considered to perform better.

Among the three types of drinking water compared here, Front Street learned after checking: the pH value of Nongfu Spring bottled water is 7.3±0.5, the pH value of Dinghu Mountain Spring Drinking Natural Water is 6.5 to 7.3, and the pH value of Kunlun Mountain Snow Mountain Mineral Water is 7.0 to 8.5. The first two are neutral, and the latter is weakly alkaline.

Having discussed acidity and alkalinity, let's now look at the softness and hardness of water. The composition of water consists of many elements. For coffee extraction, the most important are magnesium ions, calcium ions, and bicarbonate. Water containing an appropriate amount of calcium ions can better dissolve the acidity of coffee; water with an appropriate amount of magnesium ions helps enhance coffee's sweetness and aroma release. Therefore, to brew good-tasting coffee, the water needs an appropriate amount of calcium ions and magnesium ions. What people often call hard water is essentially water with excessively high magnesium and calcium content, which easily makes the taste become mixed and bitter, and therefore is not suitable for brewing coffee.

According to the WHO's Guidelines for Drinking-water Quality, hardness below 200ppm is called soft water, and above 200ppm is called hard water. For coffee brewing water, the SCA recommends a range of 75 to 250ppm, with an ideal value of 150ppm, but in practice, water that more easily brews good-tasting flavors often has a TDS below 100ppm.

When Front Street tested the above three types of water with a TDS meter, it found: the TDS measured for Dinghu Mountain Spring Drinking Natural Water was 25ppm, with the least magnesium and calcium ions; Nongfu Spring showed a TDS of 37ppm, with moderate calcium and magnesium ion content; Kunlun Mountain Mineral Water measured 322ppm, indicating that it has the highest content of dissolved substances, and after pouring water for coffee it will directly affect extraction ability, thereby causing changes in acidity, bitterness, aroma, sweetness, and other tastes.

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The above content is compiled by CoffeeHunters, a coffee news website.