A typical RO system contains four different filters that work together to clean the water. When the water enters the system, it first goes through a sediment filter, which removes any large particles from the water. After this, it goes through a pre-carbon filter, which takes out chlorine and any other organic compounds that may damage the RO membrane.
Once this initial filtration is complete, the water is ready to undergo reverse osmosis. This process works by forcing the water through a semipermeable membrane. The membrane allows water through but keeps the contaminants from coming with it.
The water then goes through one final carbon filter, which further reduces any impurities that could make the water taste or smell bad. Some systems end here and then send the water to the home. The best systems also add nutritious minerals into the water to send the healthiest, cleanest water to your tap.