This process is called “reverse” osmosis because the pressure forces the water to flow in the reverse direction (from the concentrated solution to the dilute solution) to the flow direction (from the dilute to the concentrated) in the process of natural osmosis. RO removes ionized salts, colloids, and organic molecules down to 0.0001 microns.
You can get a whole-house RO, but this would involve a very large, complex and expensive installation. Much more commonly, a point-of-use RO system would be installed under the sink and would provide filtered water at a single source. They’re great for treating water used for cooking and drinking, but they don’t usually produce large amounts of treated water — more like 3 to 10 gallons a day. For this reason RO systems are typically connected to dedicated faucets in the most popular areas of the home such as kitchen. Just like any other kind of filter technology, reverse osmosis systems require regular maintenance. That includes periodically replacing the unit’s prefilters, postfilters, and RO membrane modules.