A reverse osmosis device for purifying water from a source comprising a housing having an inlet for passage of water from the source, a first outlet for passage of purified water from the housing and a second outlet for passage of waste water remaining after purification. A first reverse osmosis multilayer assembly is disposed within the housing in fluid communication with the inlet for purification of at least a first portion of the water from the source. Water treatment chemicals can be positioned in a core about which the first reserve osmosis multilayer assembly is wound. The treatment chemicals are in fluid communication with the first reverse osmosis multilayer assembly to receive the first purified portion of water and for removal of at least chemical contaminants therefrom. A second reverse osmosis multilayer assembly is also wound on the core and is in fluid communication with the water treatment chemicals to receive the chemically purified water for purification of at least a second portion thereof. The second reserve osmosis multilayer assembly is in fluid communication with the first outlet so as to permit passage of the second portion of purified water therethrough.