Reverse Osmosis (RO) is the most popular and effective way to purify your water at home. Reverse Osmosis filter systems are inexpensive, easy to install, and will remove virtually all chemical pollutants from your water. Reverse Osmosis (RO) is a process where water is forced through a membrane with microscopic pores. Only pure water can pass through the pores. All other pollutants are flushed to the drain. Reverse Osmosis systems differ in the number of stages (3, 4, or 5 stage) but all will produce high quality drinking water.