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What Do Activated Carbon Filters Remove from Water?

What Do Activated Carbon Filters Remove from Water?


You may have come across the term activated carbon filtration during your search for different water treatment methods. Now, it’s expected that the name “activated carbon filters” kept you wondering what activated carbon filters are, how they work, and what they remove from water. Here, you’ll find out all you need to know about activated carbon filters and how to choose the best one for your home.


So, what do activated carbon filters remove from water? Activated carbon filters are particularly effective at removing chemical (organic) contaminants from tap water. They also eliminate the substances that cause foul odor and impact bad taste to water. The chemicals that may readily come to mind are hydrogen sulfide (culprit for rotten eggs odor) and chlorine (impacts bitter, metallic, or disinfectant taste to water). But how do these filters work? And do you really need one in your home?


Activated carbon filters are one of the leading water filtration apparatus in the water purification world today. And the reasons are not far-fetched. These filters can remove up to 99% of volatile organic compounds (VOCs), total suspended solids (TSS), chlorine, chloramine, heavy metals, sediments, and a host of other contaminants from drinking water.


For the next five minutes, let’s zero in on some specifics, such as how activated carbon filters help treat water and the types of activated carbon filters you can use. We will also explore how to determine if you need activated carbon filters and what type of activated carbon filter you should choose. Let’s dive right into it! 


What Are Activated Carbon Filters?

So, what are activated carbon filters? Activated carbon filters (aka charcoal filters) are filters that contain tiny bits of carbon in granular or block form, treated to be highly porous. The treatment includes injecting the carbon with steam, heat, or chemicals, creating millions of tiny pores in the carbon and increasing its surface area. After this treatment, the carbon is "activated" and becomes better at selectively trapping and removing contaminants.


Activated carbon has a vast surface area that makes them effective adsorbents that allow for the removal of contaminants and other substances. To paint a mental picture of how large the surface area becomes, as little as five grams of activated carbon can have a surface area equivalent to a 70,000 sq ft soccer field!


How Do Activated Carbon Filters Treat Water?

So, how do activated carbon filters treat water? Activated carbon filters work like magic: pass water through them, and all foul odor and bad taste are gone? Indeed, this is not obtainable with other conventional filters. Activated carbon can remove contaminants from water by two principal mechanisms - adsorption and catalytic reduction. Organic impurities are removed by adsorption, while catalytic reduction takes care of residual disinfectants.  

Here’s how activated carbon filters work. As contaminated water passes through an activated carbon filter, the filter traps/removes contaminants from the water, thereby producing purer water. Simply put, activated carbon filters attract, pull, and trap specific impurities like magnets. This is possible because the force of attraction on the carbon surface is much stronger than the attractive forces that keep them dissolved in water.


As for chemicals that do not adhere to carbon, such as chlorine, the activated carbon filters remove them by catalytic reduction (a chemical process). Chlorine molecules are converted to chloride after passing through activated carbon filters. Two factors (the flow and temperature of water) determine how effective your carbon filters will be. Optimally, the water pressure should be low and the water cool. 

Types of Activated Carbon Filters

There are different types of activated carbon filters for water filtration. They often come in two major types which are:


  1. Granular Activated Carbon (GAC Filters) and;
  2. Carbon Block Filters

Both Granular Activated Carbon filters and Carbon Block Filters are made from small bits of finely ground carbon. However, this is essentially where their similarities end. Let’s explore these activated carbon filter types. 

  1. Granular Activated Carbon (GAC Filters)

Granular Activated Carbon Filters, or GAC Filters for short, contain fine bits of carbon (millimeter-sized) loosely held together inside a cartridge or other containers. GAC filters can detect and remove contaminants that go undetected in some other filter types. Usually, the filter media in GAC filters are made from raw organic materials such as coal, coconut shells, wood, etc. Filter media made with coconut shells have the best efficiency and are the most renewable. 

GAC filters have the following advantages for water purification:

  • They are inexpensive, highly porous, and can readily be used as absorbents
  • Due to their high porosity, they offer more useful surface area per gram for physical adsorption than other filters
  • They are less restrictive than carbon block filters and therefore allow water to flow through the carbon at faster rates
  • They do not require electricity
  • They are very durable and last longer
  • They allow for the reactivation of activated carbon, unlike the single-use fine granules in carbon block filters. 

Although GAC filters are very advantageous, they do have some disadvantages. The disadvantages of GAC filters are as follows:

  • Since water seeks the path of least resistance, it can create a channel where it flows without coming in contact with the carbon filter, thereby producing water that’s not completely filtered. 
  • You may have to change the filters frequently.
  • Dumping unfiltered water into the filtered water flow is sometimes possible. 

  1. Carbon Block Filters

In carbon block filters, very fine powdered granules (usually less than or equal to 1 micron) held by binding agents (to prevent movement about each other) are used. The finely powdered granules and the binding agent are then formed into blocks after heating. There are three main types of filter media in a carbon block: the coconut-shell media, the bituminous coal media, and the wood-based media. 


Carbon block filters have the following advantages for water purification:

  1. They have carbon particle sizes 5 to 20 times smaller than the GAC filters’ carbon particle sizes.
  2. With the smaller particle size comes a higher surface area which is 7 to 10 times the surface area available in GAC filters.
  3. They prevent channeling, thereby preventing unfiltered water from getting into the filtrate. 

Carbon block filters have the following disadvantages:

  1. The compact structure of granules reduces the flow rate of water due to high contact time. Generally, it is not recommended for high flow rate applications. 
  2. The filter may have to be cleaned regularly to prevent organic matter from building up.
  3. Carbon filters may have to be replaced every 6 to 12 months, depending on use. 

What Contaminants does Activated Carbon Remove or Reduce?

Let’s take an in-depth look at what contaminants activated carbon filters remove or reduce in water. Activated carbon filters can remove physical, chemical, and gaseous impurities. According to the EPA in the United States (Environmental Protection Agency) and NSF International, activated carbon filters eliminate about 80 chemicals from water. They also effectively reduce 30 chemicals while moderately reducing 22 additional chemicals. The type and quality of activated carbon used have roles to play in how effective a filter is. 


Activated carbon filtration is the EPA’s recommended technology to eliminate pesticides, herbicides, and inorganic contaminants in water. The classes of water contaminants that activated carbon filters can remove and reduce are:

  • PFOS (Perfluorooctanesulfonic acid)
  • Pharmaceuticals
  • Phosphate
  • Chlorine
  • Chlorine byproducts such as VOCs, haloacetic acids, THMS, etc.
  • Chloride
  • Pesticides
  • Herbicides
  • Lithium

But, are there some contaminants that activated carbon filters cannot eliminate or reduce? Well, let’s find out. 

Contaminants Not Removed By Activated Carbon Filters

Activated carbon filters are not adequate for eliminating some toxic compounds. Here are some water contaminants that activated carbon filters cannot remove without highly-specialized materials or additional filtration.  


  • High levels of metals, iron, or copper
  • Pathogens
  • Fluoride
  • Radionuclides
  • Microorganisms/Biological contaminants
  • Asbestos & Arsenic
  • Calcium
  • Magnesium
  • High levels of hydrocarbons/petroleum distillates

Do You Need Activated Carbon Filters?

How can you decide if you need activated carbon filters or not? Well, it depends on the types of contaminants in your water and the concentration of these contaminants. One of the quickest and most reliable ways to test for water quality in your home is by using home water quality tests. They are also affordable and give results that are easy to understand. Check out these high-quality test kits and determine the contaminants in your water in just a few minutes. 

You can explore other options, such as requesting the annual water quality report for your area from your local water provider. But of course, this can only give you an idea of what contaminant might be in your water. Another option is sending a sample of your water to a laboratory for testing. Although the results are accurate, this procedure is time-consuming and more expensive. 


If your water tests positive for any of the contaminants that carbon filters can remove, then you absolutely need to get one. But the fact remains that most homes need activated carbon filters in addition to other types of filters (e.g., reverse osmosis filters). Why? Because sometimes, there could be accidental cases of toxic contaminant(s) getting into your water supply. If you already have a carbon filter installed, these uninvited visitors in your water supply cannot catch you unawares. 

What Type of Activated Carbon Filters Should You Buy?

Should you decide to get an activated carbon filter, there are two options to explore. 

  1. Point-of-entry (POE) filters
  2. Point-of-use (POU) filters

Let’s briefly expound on these. 

  1. Point-of-entry (POE) Filters

POE filters are connected to your home’s main water line. POE filters allow for water treatment before reaching other outlets in your home, such as the showers, kitchen, faucets, toilets, baths, etc. Whole-house filtration systems are the most common types of POE systems. When you connect activated carbon filters to Whole House RO water filters, the activated carbon filter can help protect your RO water filter and prolong its life-span. 

The iFilters Whole House & RO Coconut Activated Carbon Block Water Filter uses this POE technique to ensure that you have clean, great-tasting water in your home. They come in different particle retention sizes and are suitable for drinking water filtration applications. Here are some of the reasons why this whole house water filter is the best option for your home:

  1. Carbon block filters manufactured with NSF-certified, safe, Coconut shell activated carbon to reduce unpleasant taste, odor, chlorine, and other contaminants from Drinking water.
  2. The operating temperature range is 40 to 180 Degrees F and has a maximum pressure rating of 250 pounds per square inch (psi).
  3. Suitable for use in water dispensing applications where higher chlorine levels are present.
  4. Hydronix Coconut shell carbon blocks have great cost-to-performance value, have high chlorine reduction capabilities, excellent dirt holding performance, and offer exceptional value and performance over other similar filters in the market.
  5. Impressive water flow rate.

2.  Point-of-use (POU) filters

POU filters achieve somewhat similar results with POE filters, but they are usually installed to treat water at a single fixture. They are generally under the kitchen sink or in the bathroom. POU filters are less expensive than POE filters. Check out some great Coconut GAC filter options here!

Read This Before You Buy an Activated Carbon Filter

Summarily, before you buy an activated carbon filter, here are some things you should find out. 

  1. The type of activated carbon filter in the system (granular, carbon block, etc.)
  2. The specific contaminants the carbon filter removes and reduces
  3. The filter media the system uses (e.g., coconut shell carbon, wood, coal, etc.)
  4. Your home’s water quality (find out using any of the water testing options above)
  5. If you need a POE or POU filter
  6. Your budget

If you’re not sure how to go about any of the above, you can contact our experts. We are ever-ready to help!

Final Thoughts

Without a doubt, activated carbon filtration provides a solution to many water-contamination problems that many people currently face. You cannot go wrong if you choose to use this filtration technology in your home!

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