In daily life, many people may have heard of "soft water" and "hard water", but what is the difference between these two types of water? Which type of water is more beneficial for human health? Recently, Changchun Disease Control WeChat official account released relevant information. Simply put, the "hardness" of water refers to the content of salt substances dissolved in water, especially the content of calcium and magnesium salts. Among them, soft water refers to water that does not contain or contains less soluble calcium and magnesium compounds. Hard water refers to water that contains a significant amount of soluble calcium and magnesium compounds. Usually, rainwater, snow water, etc. in nature belong to soft water under this definition, while mountain spring water, river water, groundwater, etc. belong to hard water. If divided in detail, according to the composition of soluble salts in water, the hardness of water can also be divided into carbonate hardness and non carbonate hardness. Carbonate hardness is mainly composed of calcium and magnesium ions, carbonate ions, and bicarbonate ions. This type of hardness can form precipitates and be removed from water after being heated, so it is also known as temporary hardness; Non carbonate hardness mainly refers to the hardness formed by the combination of calcium and magnesium ions in water that exceed the content of carbonate and bicarbonate ions, and sulfate, chloride, or nitrate ions in water. This type of hardness does not change when heated, and is therefore also known as permanent hardness. The sum of the contents of calcium and magnesium compounds in water is commonly referred to as the total hardness. The World Health Organization determines the hardness of drinking water, which is the statistical total hardness. It converts the dissolved calcium and magnesium in water into calcium carbonate, and uses the calcium carbonate content per liter of water as the measurement unit. According to the hardness of water, it is divided into 7 levels: 0-75 mg/L is extremely soft water, 75-150 mg/L is soft water, 150-300 mg/L is medium hard water, 300-450 mg/L is hard water, 450-700 mg/L is high hard water, 700-1000 mg/L is ultra-high hard water, and more than 1000 mg/L is extra hard water. In daily life, soft water has many benefits for people's lives. For example, taking a bath with soft water can make hair smooth and silky, making the skin more delicate and elastic, and reducing body dandruff; Soft water laundry can make clothes soft, clean, and have a fresh color, and after drying, clothes will not become white or hard; Soft water can protect household appliances, reduce the maintenance rate of water heaters, wall mounted stoves, washing machines, and other appliances, extend the service life of water machines, and prevent scaling and blockage of water pipes installed on household walls; Soft water can also reduce the generation of dirt on the surface of daily utensils, such as cleaned tableware and porcelain, which can make their surfaces smooth and leave little or no marks. Traditionally, people believe that soft water has certain benefits, and drinking soft water can prevent the incidence of stone disease and maintain health. However, long-term consumption of soft water may lead to a deficiency of certain nutrients in the human body. The main benefit of hard water is that drinking water with hard water quality is rich in the necessary mineral components for the human body, which is an important channel for people to supplement calcium, magnesium and other components. When the content of soluble calcium and magnesium compounds in water is high, the calcium and other components dissolved in water are more easily absorbed by the human body. But there are also studies indicating that long-term use of water with high hardness may lead to kidney stones