Water is the major ingredient in a cup of tea, but it's the one we probably think about least. After all, it's just water, right? Well, not quite—there's much more to water quality than that when it comes to brewing a great cup of tea.
In China water is called the "mother of tea." That name itself indicates how important water is for brewing tea. The Chinese believe it's ideal to use the same water to brew the tea as was used to water the original tea plant. Nice idea, but not very practical unless you own or live next door to the tea plantation.
Think of it this way. From the time a tea leaf is plucked from the plant, the processes applied to it all focus on extracting water from the leaf in various ways and to varying degrees. During tea brewing, we are re-infusing the leaves with water. So we should strive to add water that balances, rather than overwhelms, the flavor of the tea.
Lo Yu, a scholar from China who lived in the eighth century, wrote the first encyclopedia of tea entitled Ch’a Ching, long considered the ultimate reference on tea. He said the highest quality water comes from slow moving mountain water. (In fact, he specified ten different springs in China ideal for this purpose.) His next choice in water quality was river water, preferably from the middle of the river; and finally, well water.
According to Lo Yu, the lowest quality water for tea comes from lakes and deep underground wells. (My sister can attest to this. Her water comes from a lake, and she always filters her water for tea. For delicate teas like whites and greens she double-filters it. Otherwise, the flavor and aroma of the tea are distorted and overwhelmed by the chemical character of the water.)
Since water quality has a profound effect—both good and bad—on the taste of tea, it’s vital to know more about the characteristics important to brewing with it. After all, there are only two ingredients in the recipe for tea. Water and tea leaves will undoubtedly play off one another in a major way.
Four important qualities in water to consider include:
The pH level of the water tells us whether it is alkaline or acidic, with a level of 7 being neutral. Pure water is neutral, and a level near this is ideal as a starting point for tea. Water with a pH less than 7 is considered acidic; greater than 7 is considered alkaline.
As a general guideline, both tap and spring water tend to be alkaline. Tap water is often deliberately made alkaline to deter pipe corrosion. Alkaline water typically doesn't produce as flavorful a tea as does more neutral water. Tea itself is mildly acidic, so the ideal pH of a brewed cup is about 5. (see Better Tea Through Testing to learn how to test the pH of your water.)
Tap water varies from place to place, not only in terms of pH. We often talk of "hard" or "soft" water. Most tap water is hard. Since hard water contains more chemicals, it is inferior to soft water for brewing tea. To clarify, we're referring to naturally soft water, not water that has been softened using chemicals in a home system.
Mineral content and chemicals impact the taste and odor of plain water, so it stands to reason they will also affect the tea in your cup. Some minerals are desirable and react favorably with tea leaves. But watch out for the following that indicate poor water quality:
Many of these chemicals would be diminished or eliminated through boiling, but for many reasons we want to avoid that (see Water Temperature).
Not surprisingly, the chemicals and minerals in your water will have a noticeable impact on your tea—not only in its taste. Look for visual cues such as cloudiness in your brewed cup, surface scum, or a dull surface. All of these are indications of unwanted chemical or mineral reactions and less than optimal water quality.
Water used for brewing tea needs to be fresh. The reason is that fresh water contains a healthy amount of oxygen (remember that oxygen is the O in H2O) that helps infuse the tea leaves to their best effect. The presence of oxygen aerates the tea and contributes to a fully flavored brew.
To ensure freshness, don't use water that has been standing in your kettle overnight. And don't use water that has already been boiled. In both cases the water quality is diminished since the oxygen has been depleted, and the resulting tea will taste flat.
The starting temperature for the water you put in your kettle to make tea is also important. Begin with cool water. The reasons are the same as why it's better to use cool water for cooking. Water heating systems introduce unwanted chemicals into the mix and change the taste in an undesirable way. Don't forget that tea leaves are particularly sensitive to chemicals.
Even if you purchase the highest quality tea, it can only reach its full taste potential if it’s brewed with quality water. The ideal situation is when the water and the tea match each other.
Everday tea brewing in our modern world is decidedly far from the traditional ideal of Lo Yu. But it doesn't mean you can't have a great cup of tea. By learning about the quality of your water, you can easily take measures to make it noticeably better. (See Better Tea Through Testing.)