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1) Activated Carbon or Charcoal Filters. These filters remove general taste and odor problems, including chlorine residue. Studies have shown that granular activated carbon (GAC) also is an effective method for radon removal. These devices do not remove nitrates, bacteria or metals, like lead. The filters are available in almost all sizes from POU units to large under-the-sink and POE or whole house units. Design greatly influences efficiency. Variations include use of powdered carbon or blocks of carbon instead of granular carbon. Units containing more carbon will usually treat greater volumes of water before replacement is necessary. Costs range from $100-$200 for the small POU filters to $400-$700 for larger POE units. 2) Reverse Osmosis Systems. A reverse osmosis (RO) unit commonly removes more than 90% of the total dissolved solids (including metals) and some organic chemicals, including many pesticides. Contaminants are removed by forcing water through a membrane having microscopic holes that allow water molecules--but not larger compounds--to pass through. Water flushes away the contaminants held by the membrane. Due to the system's use of water for flushing, RO systems are usually restricted to point-of-use installations. Costs range between $600 and $800 for an installed unit. 3) Distillation Units. Distillation units remove virtually all impurities so that the water is mineral free. Distillation, which involves boiling the water, removes minerals such as nitrate, sodium and sulfate, as well as many organic chemicals. Boiling the water makes steam that is then condensed and collected as purified water. The removal of minerals produces water than can have a bland taste. Because a kitchen location close to the point-of-use is preferred, counter or cabinet space must often be sacrificed. Prices start in the $300-$400 range for the smaller POU units. |