Because a brewed cup of tea is mostly water, the quality of your water is as important as the tea leaves themselves. Beyond just using any spring water or filtered water, there are a number of factors that will affect the taste of your infusion.

For centuries, Chinese tea aficionados have designated water from specific springs as the best water for brewing certain teas. A famous example is Dragon Well tea, which is considered best when brewed with water from the famous Tiger-Run Spring. Ancient tea masters would even have fresh water from renowned springs carried many miles in stone containers to ensure they had the best water for their tea. This is because subtle variations in the pH (acidity, alkalinity) and mineral content (Total Dissolved Solids, or TDS) of the water can affect the taste of the brew. Generally, higher mineral content can give a fuller, sweeter taste, while water with a lower mineral content can taste slightly sharper and bright. The types of minerals present will also change the taste and body of the tea. Calcium is needed for a full, sweet taste, whereas magnesium and iron are detrimental to the flavor of the brew. Distilled water should never be used because it lacks trace minerals and gives a flat, lifeless taste. The pH of the water can have similar effects, though closer to neutral (a pH of 7 is neutral) or slightly alkaline is generally considered best for tea.

If you are using tap water, some sort of filtration is usually recommended. You want to remove chlorine and other chemicals as well as sediment from your water without eliminating too many trace minerals. The composition of tap water varies from region to region and can found on the EPA or AMWA websites or from your local Water Quality Analysis. It is fun and informative to experiment using different bottled waters and filtering techniques with a favorite tea to experience the importance of good water and to find your own preferences.