Reverse osmosis

Reverse osmosis units

Unlike other types of devices that reduce impurities in the water, reverse osmosis removes water from the impurities. It does that by forcing water through a specially constructed, semi-permeable, nonporous synthetic membrane (usually cellulose acetate) that separates soluble and suspended particles from the water. The process removes a wide variety of substances from the water. More than 75 percent of such minerals as sodium, calcium and chloride may be removed from the water. Reverse osmosis also may be effective in removing fluoride, nitrate and some forms of arsenic. The membranes may last a year. Effective membrane life depends on quality of water entering the unit.

Reverse osmosis units are expensive because of the number of accessories needed to operate them. They require in-line installation and a prefilter to remove dirt and sediment. If a backflush system is employed to prevent a buildup of contaminants on the membrane, the purchase price increases.