The membrane consists of several thin layers or sheets of film that are bonded together and rolled in a spiral configuration around a plastic tub ( This is also known as a thin film composite or TFC membrane ). The material of the membrane is semi-permeable : it allows water molecules pass through while acting as a barrier to dissolved solids ( i.e. : mineral chemical contaminants ). When the feed water stream passes across the surface of the membrane, the water molecules penetrate the membrane surface, working their way around the spiral and collecting in the center tube. The remaining contaminants are concentrated and washed from the surface of the membrane down the drain.

The pores of the Reverse Osmosis membrane is 0.0001 micron. Basically 100,000 times smaller than human hair size, 10,000 times smaller than Ragweed pollens, 8,000 smaller than red blood cells, 1,000 times smaller than a bacteria and 100 times smaller than Ebola viruses.