Reverse osmosis is a process that uses pressure to force water through a semipermeable membrane. The membrane allows water molecules to pass through, but it blocks the passage of contaminants. This results in purified water that is free of impurities. The installation process for a reverse osmosis system is relatively simple and can be done by most homeowners. The water filtration systems are typically installed under the kitchen sink and consist of a filter housing, activated carbon, a reverse osmosis membrane filtration, a storage tank, and a faucet.