Water, as the medium for the body to transport and absorb nutrients, is also the carrier to excrete wastes. The metabolic process can be finished through the water circulation, where water also exerts functions of heat dissipation, body temperature regulation, lubrication of joints and internal organs, etc. Water is vital to human life.

       The hardness of water shall not exceed 450mg/L, if the hardness is too large, after drinking, it has a certain impact on human health and daily life: after bathing in autumn and winter, the skin will feel dry, cheeks tight, hair astringent. After the water heater is used for a period of time, the flow becomes smaller, and the heating time becomes longer and longer. After washing the clothes, the fibers of the clothes become brittle and hard, and the detergent smell remains. Kitchen utensils and tableware are attached with a layer of water stains that are difficult to remove after a period of use.