The water purifier according to the pipeline design level can be divided into getting tight water purifier and self-cleaning water purifier two categories. The traditional water purifier is a gradually tightening type water purifier, its internal pipeline is designed before the filter core loosely, by PP melted filter core, particulate carbon, compressed carbon, RO reverse osmosis membrane or ultrafiltration membrane, after active carbon, generally the 5 order of the first end connected. Retentate deposited on the filter inside, the need for regular manual washable, to ensure the normal operation of the machine. The other is a more advanced self cleaning water purifier, which designs two channels in the machine and adds a washing water channel. As a usual ordinary living water washing water, the water side of the inner filter, especially the membrane filter core, is scoured to clean the water through the path. The two sections of the head and tail will be lost in the water will be cut off the dirt in time and quickly discharge, the structure of the design is reasonable, to save the trouble of manual disassembly and washing, to avoid the re pollution of the organization itself, and at the same time, reduce the cost of energy consumption. The self-cleaning water purifier adopting new principle matter circulation, ready to clean out the impurity, the inner core is clean, avoid pollution two, see below the working principle.