Reverse Osmosis Systems
First investigated as industrial desalination of seawater using semipermeable membranes at UCLA over 60 years ago, the Reverse Osmosis Process has been scaled down to modify and improve small volumes of water in the home for drinking and cooking purposes. The water is squeezed under household water pressure through a semipermeable membrane and the treated water is stored in a special 2-3 gallon holding tank for use, while the reject water containing the unwanted substances is disposed of down the drain. In most cases a single faucet is installed at the kitchen sink and a line can be run to the ice maker/cold water dispenser on a refrigerator. For every gallon of treated water that is produced – approximately 3 are rejected as waste water, therefore whole house RO Systems are not only impractical but pure RO water is very aggressive and will cause problems for most household plumbing systems.
Because reverse osmosis systems operate on water pressure, the higher the incoming pressure, more water can be produced and interestingly – the purer the water will be. These systems have become very popular in recent years because of greatly increased reliability and improved membrane performance. The service interval is based on how well the water to be treated is filtered before entering the unit, the amount of water used annually, and the rejection rate (the amount of TDS present) of the membrane. Most properly installed and sized systems need to be serviced with filter changes every 1-2 years and the membrane replaced every 4-5 years.
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