Reverse osmosis is a common method of filtering water. It is often used to improve the taste, safety, and overall quality of drinking water. The filter uses an extensive and detailed process to effectively remove several contaminants from the water it is filtering. Osmosis is the process of molecules passing to a more concentrated solution through a semi-permeable membrane. Reverse osmosis is simply the opposite. Here is how a reverse osmosis filter, or RO filter, works to filter your water.


Before the water can go through the reverse osmosis process, it must be pre-filtered. Pre-filtration is used to remove some of the larger water contaminants and sediment so the thin RO membrane does not get damaged. It removes larger sediment, dissolved solids, and reduces chlorine. This first filter is referred to as the sediment filter or carbon block filter because it uses a carbon block to remove sediment. The carbon filter also improves the taste and odor of the water.

Reverse Osmosis Membrane

This is when the real reverse osmosis process happens. The water is forced through a semi-permeable membrane with great pressure. This membrane is made of a synthetic plastic material. It will let water molecules pass through, but will catch almost everything else in the water and will not let it go through the membrane. Some contaminants it catches are sodium, chlorine, calcium, bacteria and viruses, lead, arsenic, copper, nitrates and nitrites, chromium, selenium, fluoride, radium, barium, cadmium, cysts, and total dissolved solids.

Post-Filtration and Final Polish

Before the water is ready to drink, it goes through another carbon filter. This filter is used to remove any contaminants that may have slipped through the membrane as a “just in case” step. This is also one final polish before the water runs through your tap, to make sure it has the best taste and odor possible to give you the highest quality water. It is then stored until you are ready to use it. Right before it goes through your faucet, it goes through one last activated carbon filter to remove any tastes or odors that may have accumulated while it was sitting in the storage.