Abstract: The present invention relates to RO water purifiers. An object is to provide a simpler waterway as compared to prior art, that can be used in RO water purifiers. A further object is to provide an RO purifier comprising a waterway in which one or more components may be easily replaced. Disclosed is a reverse osmosis (RO) water purification device comprising an integrated waterway. The objects are met through the RO water purifier of the invention comprising a waterway which has pre-filter component, an RO component, and a post-filter component. The pre-and post-filter components each comprise pilot-operated solenoid valve having an electro-mechanical solenoid and a hydraulic part which is integrally molded with the component. The pre-filter component is removably connected with the post filter component and the post filter component is removably connected with the RO component via a removable connector.