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Water filters may be able to remove certain contaminants from tap water, but cannot effectively eliminate all viruses or bacteria. Filters must be replaced regularly and according to the manufacturer’s directions. Without proper maintenance, bacteria can build up in the filtration products and contaminate drinking water. Point-of-use filters are installed on household water faucets. Point-of-entry filters are installed where the water line enters the house to treat water being used throughout the house.
There are several different types of water filters. No one filter can eliminate or reduce all possible contaminants. Common types of filters include:
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Filter Type
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Possible Actions
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Adsorbent filters (e.g., carbon, charcoal)
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Substances adhere to the surface of the filter. These filters may remove certain chemical contaminants, metals (e.g., lead, mercury), parasites and sediment. They do not remove microorganisms (e.g., bacteria, viruses). |
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Reverse osmosis systems
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Pressure reverses the flow of water through a membrane, leaving contaminants behind. It removes microorganisms (including Cryptosporidium), minerals, organic and inorganic chemicals, as well as any water color, taste and smell.
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Distillation systems
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These systems heat water until it boils, and then water vapors are collected and condensed back into water. Microorganisms are killed during this process (including Cryptosporidium). These systems may remove metals, minerals and some organic materials. |
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Ultraviolet systems
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Ultraviolet light is used to disinfect water. These systems may kill most microorganisms, depending on the amount of ultraviolet light applied.
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Water may be characterized as hard or soft, depending upon its mineral content. Hard water is high in calcium and magnesium, which has been dissolved from soil and rainwater. Soft water has greater amounts of naturally occurring sodium and potassium.
Water softeners contain sodium ions, which remove and replace the calcium and magnesium in hard water. How much water softener to use depends on the mineral content of the hard water. Local health departments have information about the mineral content of public drinking water. Soft water is often considered more desirable for household use because it makes soap lather better and helps dissolve contaminants (e.g., lead, cadmium) from older plumbing pipes. Water softeners are not recommended for people monitoring their sodium intake. |
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