Water naturally passes through a membrane from the more diluted side toward the more concentrated side by osmosis. But with the added influence of water pressure, an R/O can make the water move through the semi-permeable membrane in the opposite direction from the concentrated to the more dilute side (hence reverse osmosis). This allows the water to pass through the membrane while most of the contaminants remain behind and are flushed down the drain.
Benefits: New r/o membranes can remove up to 95% contaminants; can be used on water sources with a high mineral content.
Limitations: Makes water very slowly, requiring the use of a storage container; produces a considerable amount of waste water – 5 to 15 gallons of waste water for every 1 gallon of R/O water produced; contaminant removal eventually drops to 70% at which time most manufacturers recommend replacing the membrane; is not recommended for use on water known to contain pathogenic bacteria.
Used in combination with sediment filters and activated carbon filters to protect the membrane and to improve the taste of the water as it exits the storage tank.