Activated carbon is one of the most widespread filter media that can be found in almost any water filter system, be it a reverse osmosis system or a regular under-sink water filter. Their high microporosity and large surface area makes carbon filters very good at adsorbing volatile organic chemicals, herbicides, pesticides, chlorine, disinfection by-products and a range of other chemicals. Apart from their advantage of being a highly adsorbent material, carbon is also a natural filtration media that adds nothing to water, leaves no aftertastes, and actually significantly improves the taste of water.

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Are activated carbon water filters safe? Should you be aware of any concerns given that they are one of the most widely used natural filter media? In this article we’re going to address the most common concerns people have with respect to activated carbon filters, and how you can deal with these concerns.

The most commonly mentioned concern with activated carbon filters are carbon fines, which are suspended black or grey colour solids that often appear in your water when a new filter is installed, and they are more frequent in granular activated carbon filters. These carbon fines are not harmful, but they are certainly an unpleasant sight. You can get rid of these by generously flushing the filters to wash them away.  

Limitations of carbon water filters

There is no filter media that can effectively deal with any and all kinds of contaminants. This is why you’ll often see different filters combined together in a single multi-stage filter system that can offer protection against more types of contaminants. Just like the reverse osmosis membrane, for example, does not remove chlorine, activated carbon will not remove dissolved inorganic chemicals, certain bacteria or certain heavy metals. In order for a carbon filter to be effective, it has to contain enough carbon, which has to be in contact with water long enough to be able to remove contaminants.

Risks associated with bad filter maintenance

Carbon filters are known to harbour bacteria, which can build up and make their way into your water if filters are not replaced at the recommended intervals. Apart from bacteria, contaminants can also saturate the filter, which will make your filter ineffective. This is why it’s crucial to observe the proper filter maintenance guidelines and replace your filters regularly. Some carbon filters are impregnated with trace amounts of silver, which is known to inhibit bacterial growth.


Carbon filters are safe, however, as you can see from the above, improper filter maintenance can cause problems. Buy only NSF certified, reputable water filters and make sure you change your filters regularly.