Hardness of Water

What is water hardness?

Hardness refers to the amount of calcium and magnesium ions dissolved in 1000ml of water. The World Health Organization (WHO) drinking water quality guidelines define it as follows:

• Soft water: hardness 0-60 mg/liter
• Moderately soft water: hardness 60-120 mg/liter
• Hard water: Hardness 120-180 mg/liter
• Very hard water: hardness of 180 mg/liter or more

Most of the water in Japan is soft water. It is said that differences in hardness affect the aroma, color, and flavor.

The hardness of tap water in Kyoto City is around 40. (Reference: Kyoto City Waterworks Bureau)

What kind of water goes well with Japanese tea?

The water that is best suited for Japanese tea is soft water with a hardness of around 30 to 80 mg/liter. Japan's tap water is soft to medium soft, making it suitable for Japanese tea. Japanese tea is enjoyed for its balance of umami, astringency, and bitterness. This is because high hardness suppresses the bitterness of tea.

Japanese tap water is disinfected with chlorine, so to make delicious tea, it is necessary to remove the chlorine smell. Always boil tap water for 2-3 minutes before using. You can also remove the chlorine by leaving it to sit for 4-5 hours. If you use a water purifier, it is also recommended to boil the water before using it.