Activated-carbon water filters are the most popular home water treatment devices. Carbon filters remove organic compounds such as industrial solvents, pesticides, chlorine and chlorination byproducts. As you may know, activated-carbon units are usually the easiest to install and maintain with ongoing costs often limited to filter replacement.

How They Work

Activated-carbon water filtering works by removing contaminants from water by adsorption, or the attraction and accumulation of one substance on the surface of another. In activated carbon processes, the adsorption surface consists of pores, or small openings, created in carbon granules during the activation process. In general, high surface area and pore structure are the prime considerations in adsorption of organics from water. Carbon water filters work best when they are able to operate slowly.

Effectively removes:

Chlorine, organic chemicals, pesticides, radon, odors and bad taste

May help with:

Sediment and turbid water

May not remove:

Microbial contaminants, sodium, nitrates, lead and other heavy metals, fluoride and hardness minerals


  1. Activated-carbon provides an ideal medium for the accumulation and growth of bacteria. A unit containing a bactericide, usually a silver compound, will minimize this risk.
  2. Contaminant breakthrough can occur if the filter is used after the carbon bed is exhausted. When breakthrough occurs, previously‐adsorbed contaminants are released from the bed and contaminant levels in the product water can exceed those in the source water. Changing the filter regularly can eliminate this risk.
  3. Activated-carbon removes radon, however as the radon decays in a filter, long‐living radiation is produced. The amount of resulting radiation corresponds to the level of radon and other radioactive materials in a water supply and the amount of water used.

What’s In My Water?