Activated Carbon Filters: What Are They And How Do They Filter Water? - Filter Flair

Do you know what activated carbon filters are? If not, you're in for a treat! Activated carbon filters are a fantastic way to improve your water quality. This blog post will discuss what and how activated carbon filters work, and the benefits they offer. So, if you're curious about these amazing filters, read on!

Activated Carbon Filters are one of the most widely used products in water purification, but if you are just learning about water filters or you’re unfamiliar with the different types of filters out there, this can be just another bit of jargon that isn’t quite clear on what it actually is.

What Is Activated Carbon?

Activated carbon is a form of carbon that has been treated to increase its porosity and thus its surface area. This makes it ideal for adsorbing organic compounds from liquids or gases. It is used in various applications, including water purification, air filtration, and medical procedures.

The most common method of activation is chemical activation, which involves treating the carbon with an oxidizing agent. This creates a network of pores on the carbon's surface, increasing its surface area. Activated carbon can also be produced by physical activation, which involves heating the carbon to high temperatures. 

Activated carbon is a form of carbon that is commonly used to remove contaminants from both air and water, and is widely used in water filtration systems across the world. Typically sourced from bamboo or coconut husks, the carbon is put through ‘activation’ which involves either a chemical or thermal process to greatly increase its surface area along with the amount of small, low-volume pores that are then able to adsorb contaminants.

To put this into perspective, one gram of activated carbon has a surface area of over 3,000 square metres - almost half a football pitch!

How Do Activated Carbon Filters Purify Water?

Activated carbon filters are one of the most effective ways to purify water simply due to their incredible surface area. As water passes through an activated carbon filter, the contaminant molecules are drawn into the millions of pores on the surface area of the carbon, trapping them inside whilst the water continues to pass through, effectively leaving the carbon purified.

Beyond this physical adsorption process, activated carbon also facilitates chemical reactions that further purify water. Most commonly, as chlorine comes into contact with activated carbon, the molecules react to form chloride ions which effectively removes chlorine from the water.

There are several factors that affect the level of contamination activated carbon filters can remove. The quality of water such as the amount and type of contaminants it holds, the water temperature, its pH and contact time all have an effect on its effectiveness.

In addition to this, the specific type of carbon also affects the level of filtration it can provide. For example, Granular Activated Carbon has larger holes that are more effective at trapping bigger, heavier particles molecules whereas 

Two Main Types of Activated Carbon Filters

There are several classes of activated carbon filters which are broadly categorised by size, method of preparation and application. Whilst there are up to 150 different types, the two most common types used in domestic water filtration are Granular Activated Carbon (GAC) and Carbon Block filters.

Granular Activated Carbon (GAC) Filters

GAC filters are often used in whole-house water purification systems and can effectively remove contaminants from water. However, they can also remove beneficial minerals from water, so it is important to choose a GAC filter to remove the specific contaminants in your water.

Granular Activated Carbon filters contain a granular form of carbon that is loosely contained within a filter cartridge. With a lower surface area and larger pores, GAC can be preferred due to its higher flow rate whilst still offering an effective level of contaminant reduction. 

Commonly used in water filters for refrigerators and under sink filter systems, GAC filters can be susceptible to bacteria growth due to channelling, where stagnant water can be held in pockets of the GAC media providing the ideal setting for bacterial growth. This is why it’s always recommended to change your filter when recommended by the manufacturer, commonly every 6 months!

Solid Block Carbon Filters

Another type of activated carbon filter is a carbon block filter. These filters are made of compressed carbon, which makes them more effective at removing contaminants than GAC filters. Carbon block filters are often used in reverse osmosis systems and can effectively remove many contaminants.

Carbon Block filters contain densely packed blocks of Powder Activated Carbon (PAC) and GAC, giving it a much smaller pores and higher surface area compared to GAC filters.

This type of filter is much more efficient and effective in reducing a wide range of contaminants due to the smaller pore size, however due to this the flow rate is reduced as water passes through slower than it would through a GAC filter.

Which Impurities can Active Carbon Filters Remove and Reduce?

As you have read, activated carbon is one of the best methods of water filtration and can remove several different contaminants from water. 

Overall, carbon filters can remove at least 81 chemicals and are also effective at reducing a further 52. According to research conducted by the US Environmental Protection Agency, activated carbon is the only material that removes:

  • all 32 identified organic contaminants including THMs (by-products from chlorine know to be cancerous)
  • all 12 identified herbicides
  • all 14 pesticides (including nitrates and glyphosate AKA RoundUp)

For most users, the most obvious chemical removed by activated carbon filters is chlorine, which gives drinking water a chemical taste and smell. By removing this, the quality of drinking water is improved greatly and makes tap water much more palatable.

Whilst there isn’t any single filter that is capable of removing every contaminant from water, activated carbon offers the closest thing to this and can be easily installed in every home.

The bulk of public tap water in Europe and North America is rigorously managed, tested, and certified as safe to drink. To make it safe, chlorine is added, which may give it an unpleasant taste and odor. Activated carbon filters work wonders at removing chlorine and the bad taste and odor it generates. High-quality activated carbon filters may remove up to 95% of free chlorine.

Chloride, a calcium and sodium mineral, should not be confused with chlorine. When activated carbon is used to filter water, the amount of chloride in the water may actually increase slightly.

Chlorine By-products

The most frequently stated issue regarding tap water is the presence of VOCs (volatile organic compounds) from chlorine, such as THMs, which have been identified as potentially carcinogenic. Activated carbon exceeds all other filtration technologies in removing them. According to the EPA, it eliminates the 32 most common chlorine by-products. Total THMs are the most commonly tested THMs in tap water reports.

Chloride (Cl-)

Chloride, a naturally occurring mineral, aids in the maintenance of proper blood volume, blood pressure, and bodily fluid pH. Too much chloride in the water, on the other hand, may cause it to taste salty. Chloride is a naturally occurring element in tap water that has no negative health consequences. It is a phase in the chlorination process that safeguards drinking water against harmful viruses and bacteria. Although activated carbon can reduce chloride by 50-70%, it is not essential to filter or remove it. Chloride levels can even grow in extreme cases.


Weeds can make their way into groundwater, lakes, rivers, the ocean, and even tap water despite treatment. Pesticides are chemicals that are used to control pests such as weeds. Chlordane, Chlordecone (CLD/Kepone), Glyphosate (Round-up), Heptachlor, and Lindane are among the 14 most common pesticides studied for removal by activated carbon. This also includes nitrate (se below).


Herbicides, sometimes known as weedkillers, are chemicals used to control undesired plants. Activated carbon filters like the Doulton Chlorasyl Ceramic Filter has been tested for its capacity to remove 12 of the most commonly used herbicides, including 2,4-D and atrazine.

Nitrate (NO32-)

Nitrate is one of the most important chemicals for plants. It is high in nitrogen, which is essential for plant growth. Nitrate is not known to damage adults unless it is present in extremely high concentrations. Too much nitrate in water, on the other hand, can cause methemoglobinemia, popularly known as "blue baby disease" (Lack of oxygen).

Fertilisers, septic tanks, and manure storage or application methods are the main sources of nitrate in drinking water. Depending on the quality of the filter, activated carbon can reduce nitrate by 50 to 70%.


PFOS, a synthetic molecule, is used in a variety of products, including metal plating, stain repellents, and firefighting foam. With a few significant events in North America and Europe, it has over the years found its way into the environment and drinking water sources. The Environmental Directorate of the OECD reported in 2002 that "PFOS is persistent, bioaccumulative, and hazardous to mammalian species." It has been discovered that activated carbon may successfully remove PFOS, including PFAS, PFOA, and PFNA.

Phosphate (PO43-)

Like nitrate, phosphorus is necessary for plant growth. Strong corrosion inhibitors include phosphate. There are no health hazards associated with high phosphate concentrations in humans. Phosphates are frequently added to drinking water by public water systems (PWSs) to stop lead and copper from pipes and fixtures from leaching into the water supply. 70–90% of phosphates are routinely removed using high-quality charcoal filters.

Li+, or Lithium

Drinking water contains lithium by nature. Lithium is a substance that is used to make antidepressants, despite its extremely low prevalence. On the human body, it hasn't manifested any negative effects. Geothermal waters, oil-gas field brines, and continental brine water all contain lithium.


Medications and their metabolites have been released into wastewater on a reasonably constant basis as a result of the widespread use of pharmaceuticals. Given that the concentrations of pharmaceuticals detected in drinking water are many orders of magnitude lower than the minimum therapeutic dose, current observations suggest that it is extremely unlikely that exposure to very low levels of pharmaceuticals in water would result in appreciable adverse risks to human health. The effluents from poorly regulated manufacturing or production facilities, notably those connected with generic medicines, may contain pharmaceuticals that are dumped into water sources. 95% of medications are removed by high-quality carbon block filters.


Microplastics are produced as a result of several sources of plastic waste. It is challenging to pinpoint the specific impact of microplastics on human health for a number of reasons. Plastics come in a variety of forms, and they may or may not contain various chemical additions. Plastic garbage does not break down like natural materials do when it gets into waterways. Instead, plastic waste disintegrates into tiny fragments as a result of exposure to the sun's rays, a reaction with oxygen, and degradation from natural components like waves and sand. The smallest microplastics found in open reports have a 2.6 micron diameter. All microplastics larger than 5 microns can be removed with a 5 micron carbon block, such as Omnipure Q5586 Water Filter.


If you are concerned about any of these impurities in your drinking water, an active carbon filter can be a great way to reduce their levels and protect your health.


Activated carbon filters are the most commonly used types of water filtration units, and clearly for good reason! With a range of different types that effectively remove such a wide range of contaminants, you can be sure that you’re giving you and your family the best quality water when using one of these filters.

An activated carbon filter is a filtration system that uses activated carbon to remove contaminants from water or air. Activated carbon filters are often used in conjunction with other filtration systems, such as reverse osmosis or ion exchange systems, to provide better quality water or air. Active carbon filters can reduce the levels of many contaminants, including chlorine, volatile organic compounds (VOCs), and pesticides.

Filter Flair has you covered if you're looking for high-quality activated carbon filters. We offer a wide selection of activated carbon filters that meet your needs. Shop now and get started on improving the quality of your water or air today!


Are carbon water filters safe?

Carbon water filters are completely safe and will only improve the quality of your water, as long as they are changed according to the manufacturer's recommendation.

Always look for 3rd party quality approvals from organisations such as NSF or WRAS which shows it has met stringent quality standards.

When and where should you use a carbon filter?

Carbon filters are most commonly used in refrigerators, under sink filter systems and filtered water jugs for drinking water, as well as in shower filters and whole house filter systems.

Essentially, carbon filters can and should be used wherever there is a need to purify water whether it is used as a standalone filter or in conjunction with other elements, such as in a reverse osmosis system.

Carbon filters have multiple applications. At the point of use (POU), it can be used to filter water before drinking or cooking (POE). Some shower heads include carbon filtration to prevent chlorine gas inhalation during showering. Carbon filters can be incorporated into reverse osmosis (RO) and ultrafiltration (UF) systems. In conjunction with a UF system, a carbon filter decreases lead and organic and chemical contaminants.

Before installing a water softener to soften municipally treated water, a carbon filter should be installed. By eliminating chlorine before softening, the lifespan of the softer resin can be extended. Catalytic carbon must replace chemical disinfectants to extend the life of water-using devices such as your tankless water heater. Chloramines can harm rubber gaskets, seals, and O-rings.

How often should you change your carbon filter?

When looking to replace your carbon filter you should always check the manufacturers guidelines, which typically provide a litre capacity as well as a timeframe for the filter to be changed.

Most filters are recommended to be changed every 6 months or once the capacity has been reached, whichever comes first.

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