Purified water has a very high degree of cleanliness and contains very few impurities. It can be used as a preparation component, also can be used to clean equipment and instruments, and for in vitro diagnosis. It is an important component in GMP quality management and verification of pharmaceutical enterprises. Therefore, in the view of Sundry, the essence of maintaining the quality of the purified water system is to control the possible pollution sources in the pharmaceutical production process through a good system design to ensure the quality of the produced water.