What is the difference between hard water and soft water? 【Basic Knowledge】

Does the name change for the same water between "hard water" and "soft water"? Explaining the secrets of hardness and scale prevention!

■What is the difference between hard water and soft water? "Hardness" is an indicator that represents the total amount of calcium and magnesium contained in water. These two elements react with soap in water and tend to create insoluble soap scum, making them components that have historically been used as a standard for hardness due to their potential to cause equipment troubles. ■Are the standards for hardness different by country? In Japan, water with a hardness of less than 100 mg/L is called "soft water," while water with 100 mg/L or more is called "hard water." On the other hand, the WHO guidelines classify water more finely: less than 60 mg/L is "soft water," 60 to less than 120 mg/L is "moderately soft water," 120 to less than 180 mg/L is "hard water," and 180 mg/L or more is "very hard water." ■Why are boilers troubled by "scale"? Calcium carbonate has properties that are opposite to many substances. While most substances dissolve more easily in water as the temperature rises, calcium carbonate becomes less soluble as the temperature increases. Therefore, when water is heated and concentrated in a boiler, the calcium that cannot dissolve adheres to pipes and heat transfer surfaces as scale. Facilities that use hard water require diligent water quality management.

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