Reverse osmosis water filter is the only water filtration method that removes most contaminants, minerals and substances from drinking water at a molecular level. It is also one of the most effective ways to address unpleasant tastes and odors in water. It is generally just one step in a comprehensive water treatment system for homes using city or private well water, and it can be combined with other methods like carbon filtration to remove bad taste and odors and ion exchange to reduce hardness.

Reverse Osmosis

The process of osmosis is when liquid moves from areas of low concentration to higher concentration, passing through a semipermeable membrane in the process. This creates a high concentration of solute on the opposite side of the membrane from the pure solvent, and leaves behind a lower concentration of solute with the pure solvent on the other side. Reverse osmosis takes this natural phenomenon and reverses it, using pressure to unnaturally force water through the membrane, keeping any substances on one side of the membrane and leaving only clean drinking water on the other. This technique requires a tremendous amount of pressure—from 200 to 400 pounds-per-square-inch (psi) for brackish water reverse osmosis, or SWRO, and even more for removing salt from seawater or desalination of fresh or brackish waters.

What is Reverse Osmosis? A Guide to RO Water Filtration

This immense amount of pressure causes a lot of waste water to be lost during the osmosis process, which can be up to 70%. Because of this, reverse osmosis systems are only recommended for those with a large quantity of extra drinking water they need to dispose of, or who have specific reasons they require highly purified water.