The reverse osmosis system itself is fairly simple, consisting of a series of tube containing the membranes with a high pressure pump to force the water through the system. An alternative would be to dose the system with chemicals to remove the chlorine and hold the hardness ions in solution. After the carbon filter, the water is passed through the membranes where the concentrate is recycled back to the front of the system for another pass and a bleed is taken off this line to drain. This recycling allows very high system efficiencies. A sidestream off this line feed a DI bottle service for DI water.
Membranes are very good at rejection high molecular weight compounds and multivalent ions.
The amount of leakage is determined by the reject ration. The reject ratio changes over the life of the membrane and leakage increases. When they do, this will plug the very small pores of the membrane. Organic compounds can also plug the pores. Once plugged, the flow decreases and the membrane must be cleaned.