If not tap water, what kind of water should be used for brewing tea?

As an enthusiastic gongfu-cha tea brewer and a heavy rock tea drinker, I'm always searching for the best water source for brewing my teas. You might wonder, isn't tap water sufficient since we consume it daily? Definitely not, because most tap water is hard and contains many unwanted minerals and chlorine.

What kind of water should be used for brewing tea, then? This needs to be explained from the four key elements of water itself.

The Four Elements of Water

Water quality significantly impacts the quality of the tea liquor, mainly in four aspects: water hardness, pH value, TDS value, and freshness.

1. Water Hardness

This refers to the concentration of calcium and magnesium ions in the water. Studies show that brewing rock tea with hard water makes the tea liquor dark and cloudy, causing irreversible auto-oxidation of thearubigins, which affects the tea’s quality. Therefore, using clear soft water with low calcium and magnesium ion content can better bring out the flavors of Wuyi rock tea.

2. pH Value

The pH value indicates the acidity or alkalinity of water. Water with pH=7 is neutral, pH<7 is acidic, and pH>7 is alkaline. The color of tea liquor is susceptible to pH. The reference pH value for brewing oolong tea is between 6.0 and 7.5, which is slightly acidic or slightly alkaline water. The pH value should fall within this range for brewing Wuyi rock tea.

3. TDS (Total Dissolved Solids)

TDS indicates the amount of dissolved solids in water per liter. Generally, the TDS value of tea liquor is between 110 and 180. Suppose the TDS value of the brewing water is too high. In that case, it suppresses the aroma and flavor of the tea, restricting the dissolution of tea minerals, which is not conducive to fully expressing the tea’s flavor. High TDS water also increases hardness, making the tea liquor dark and cloudy, leading to irreversible auto-oxidation of thearubigins.

4. Freshness

This refers to when the water left the source and was bottled. Fresher water contains higher levels of carbon dioxide and oxygen, which promote the decomposition of high molecular proteins and amino acids in the tea, enhancing the aroma and freshness of the tea liquor.

The Five Common Types of Water

1. Tap Water

It is widely agreed that untreated tap water is unsuitable for brewing tea. Tap water often has a high TDS value and undergoes chlorination. According to national standards, the residual chlorine content must be ≥0.3mg/L, but tea evaluation water requires <0.1mg/L. Untreated tap water may carry a chlorine smell and accelerate the oxidation of polyphenols in the tea liquor, leading to a dull appearance. Therefore, tap water is not suitable for brewing tea.

2. Distilled Water

Distilled water, also known as purified water, lacks oxygen and carbon dioxide due to the distillation process, making it less suitable for brewing tea.

3. Purified Water

Purified water can either be self-filtered or commercially bottled. It contains no impurities, has a TDS value below 10, and a pH between 6-7, making it weakly acidic soft water. It preserves the original characteristics of tea without adding or subtracting from its qualities. Self-filtered or commercially bottled options can be used depending on the water purity.

4. Mineral Water

Mineral water contains added food-grade mineral salts. Using mineral water with additives for brewing natural tea, especially Wuyi rock tea, is not recommended as it can interfere with the natural flavors. It typically has a high chloride content, making it unsuitable for tea brewing.

5. Natural Water

Natural water includes natural mineral water, spring water, mountain spring water, and surface water like rivers, lakes, and reservoirs. These vary in mineral content and suitability for tea brewing based on their TDS and mineral composition.

Identifying Suitable Water Types

When choosing water for brewing tea, consider the TDS, calcium, magnesium, sodium, and pH values indicated on the packaging. High levels of calcium and magnesium increase water hardness, while excessive sodium can impart a salty taste, disrupting the balance of the tea’s flavor.

For example, brands like Evian mineral water have high TDS, calcium, and magnesium levels, making them unsuitable for brewing rock tea. In contrast, water brands with spring water have appropriate TDS and pH levels and are often found suitable for brewing tea.

As for me, I am very particular with the taste of my rock teas. Two types of water are suitable for brewing rock tea: purified and natural. Purified water is ideal for evaluating the characteristics of lighter-roasted rock teas within 10 years of aging. For medium- to high-roasted rock teas or teas aged over 10 years, bottled natural mineral water, spring water, or mountain spring water with specific parameters is recommended to enhance the tea’s flavor and aroma. And this could be applied to all tea types.