What is a Reverse Osmosis Water Filter?

Reverse osmosis is forcing a fluid through a filter under pressure. It is a common method of purifying water and is typically performed on a small scale in the United States. Reverse osmosis water filters are often used to make drinking water and water for aquariums.

Overview

A reverse osmosis device pushes the water through a membrane, leaving behind most of the particles that are smaller than the filter. This produces water with a greatly reduced content. Reverse osmosis is so-named because this process is the opposite of regular osmosis, in which particles in a solution move from an area of low concentration to an area of high concentration without pressure. A reverse osmosis water filter is commonly used to remove the chemicals in tap water that are harmful to coral in an aquarium.

Filter

The filter used in reverse osmosis is generally a thin film composed of a composite material. The essential feature of the filter is the dense polymer in the middle of the membrane. A reverse osmosis device can filter water from a variety of sources without changing this membrane.

Pressure

The concentration of particles in the water determines the amount of pressure the reverse osmosis water filter must apply to be effective. The amount of pressure must be greater than the osmotic pressure solution, meaning that a greater pressure is required to filter water with a higher concentration of particles. Brackish water requires 30 to 250 pounds per square inch of pressure, while seawater requires 600 to 1,000 psi.