Water purification tea will form a film on the surface because of the high mineral content in the water in this area, and another major feature of the water purifier is that some minerals will be retained in the effluent. When the minerals in water and theophylline, tea polyphenols in tea, etc; Antioxidants and other natural compounds will form a film on the water surface. The film formed by this natural substance is good for human body, so please don't worry.