Block filters can be fabricated to have such a fine porous structure that they filter out coliform and associated disease bacteria, pathogenic cysts such as giardia, and lighter-weight VOCs. Block filters eliminate the problem of channeling. Also, they are so dense that they do not allow the growth of bacteria within the filter. They should be replaced every six to twelve months. Block filters need to be replaced more frequently.
Carbon filters come in several styles.
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