How do Charcoal Water Filters Work?

charcoal water filter

Many home water filtration systems feature charcoal-based filters, but have you ever wondered exactly how charcoal is used in a filtration system to filter water? Charcoal is a great natural ingredient for water filters, but the charcoal actually used to filter is called activated charcoal, which is different from the charcoal you use in your backyard bbq. Activated charcoal is generally crush up into small pieces, which allows for more water to pass over the surface area of the charcoal, and expose more water molecules to the pores in the charcoal. Activated charcoal purifies through the process of adsorption (not to be confused with 'absorption'), which is where the charcoal chemically binds impurities in the water to the surface of the charcoal filter particles rather than physically absorbing them. Activated charcoal is an ideal water filter because it removes toxins from the water without stripping the water of salts and other important minerals. These adsorption qualities of activated charcoal is why you hear of people using it to try and clean out their system from toxins and impurities like alcohol, and use it as a hangover treatment. There is no real science that supports this idea.

So, for water filtration, there are three primary processes:

  1. Mechanical filtration – This is the process of forcing water, either through pressure or gravity, through a fine membrane to physically or mechanically remove particles and sediment from your water. Small debris like sand, dust, dirt and other sediments are the first foreign substances that need to be removed from water during the purification process. Some filters will emphasis the size of the holes in their filters and membrane by pointing the size of filtered out material in microns. Generally speaking, a 1 micron filter in quite fine and will remove most if not all particulate, as well as small bacterial particles called cysts like Giardia and Cryptosporidium.
  2. Carbon/charcoal filtration – Most water filter systems use the pores within carbon or charcoal to remove the unpleasant tastes and odors which can be caused by a variety of factors, including chlorine and other chemicals, old underground pipes and unstable levels in water tables and aquifers. This second layer or level of filtration ensures that your water looks and tastes as appealing as it can.
  3. Removal of some minerals, including limescale – Limescale and other minerals can accumulate and is not good for your water using appliances like your coffee maker or dishwasher.

Some of the benefits of charcoal-based filtration:

  1. The good stuff isn't filter out of your water, only the bad stuff that might be lingering in your pipes like copper, mercury and cadmium
  2. Your water will taste better. While important in disinfecting your water, chlorine has no value to your mouth and tongue.
  3. Very inexpensive compared to bottled water
  4. Easy maintenance – by replacing the filter every 12 months, you can help make sure the water you drink from you home system will taste as good as it can.
by Steve Jortsman