RO is the most convenient and effective method of water filtration. It works by squeezing water through a semi-permeable membrane, thereby screening contaminates down to .0001 of a micron in size with a micro organism rejection rate of 99.95%. While the screening of inorganic contaminants, such as harmful heavy metals and chemicals, is 95-99%.

Non-RO water filters are much less effective, and the pore size on these filter media are much bigger, generally 0.5 - 10 micron. They can filter out coarse particles, sediments and elements only up to their micron rating. Anything finer and most dissolved substances cannot be filtered out. As a result, water is far less clean and safe compare to reverse osmosis filtration.

This technology is also used to make bottled water; it is also the only technology capable of desalinating sea water, making it into drinking water.