Q3 What is the RO membrane made of and how does it work?

The RO membrane is made of a very thin film (which does the actual filter separation) embedded on a layered supporting sheet. (Kind of like a thin sheet of plywood, with a very thin veneer) This configuration is known as “Thin Film Composite” or TFC membrane. The membrane is rolled in a spiral configuration around a plastic tube, and pure water flows to the center tube where it is collected. Impure water flows across the surface of the membrane and out the end of the membrane tube to the drain.