Abstract: Water from a source is fed to a reverse osmosis unit having a membrane which divides the stream into a first permeate product and a first concentrate. The first permeate product is stored in a tank until a selected quantity is collected and then the source is disconnected from the pump which next delivers water from the tank to the reverse osmosis unit to divide the stream into a second permeate product and a second concentrate. In one version of the equipment the second permeate is processed by a different membrane than that producing the first permeate. In another version, the same membrane is used, the second permeate product is stored, and the second permeate product is later run through the reverse osmosis unit to produce a third permeate product and a third concentrate.