Impurities removed by the RO System are washed down the drain. Unlike other filters, the Reverse Osmosis membrane is self-cleaning. As water flows through the RO membrane, it is divided into two streams. One stream is pushed through the membrane by your water pressure. The second stream flows to the drain carrying dissolved pollutants, rejected salts, and contaminates. This means very little debris accumulates on your membrane allowing it to last for about a full year of use.