Activated carbon water filters are one of the most popular and effective ways to improve water quality. Known for their ability to remove chlorine, chemicals, and unpleasant tastes and odors, they offer a simple yet powerful solution for cleaner, better-tasting water. In this guide, we’ll explore how activated carbon filters work, the different types available, their advantages and limitations, and how to get the best performance from your system.
What are activated carbon filters?An activated carbon water filter is a filtration system that uses processed carbon to remove chlorine, foul taste, and bad odor from drinking water. The carbon is "activated" through a high-temperature process that creates millions of tiny pores across its surface, giving it an incredibly large surface area.
How do carbon water filters work?
Carbon filters remove contaminants through a process called adsorption, which causes particles to stick to the surface of the carbon (similar to how Velcro works). Many organic compounds and contaminants are naturally attracted to the carbon’s surface.
Carbon filters are highly effective because of their porous structure. They contain millions of microscopic pores that provide a massive surface area for trapping impurities. As water flows through the filter, contaminants like chlorine, volatile organic compounds (VOCs), and unpleasant tastes and odors stick to the carbon.
The pores in carbon filters are measured in microns—smaller pores mean finer filtration. Lower water pressure and slower flow rates allow more time for contact with the carbon and improve filtration performance.
Where are carbon filters used?Carbon filters can be used as point-of-entry (POE) systems to filter the whole house or point-of-use (POU) filters to clean water before you drink or cook with it. Refrigerator water filters often contain a blend of sediment and carbon filtration. Some shower heads include carbon filtration to prevent negative chlorine effects on skin and hair. Carbon filters are also part of a reverse osmosis system or an ultrafiltration (UF) system. A carbon filter added to a UF system provides organic and chemical particulate reduction along with lead reduction.
If you use a water softener to soften water treated by a municipal plant, then you should install a carbon filter before the water softener. If chlorine is removed prior to softening, then the softener resin lasts longer. Chloramines can cause O-rings, gaskets, and rubber seals to deteriorate, so removing chemical disinfectants with catalytic carbon helps water-using appliances, like your tankless water heater, last longer.
Advantages of carbon filtrationActivated carbon water filters are a popular choice for good reason. They offer a range of benefits that make them both practical and effective for everyday use.
Improves taste and odor
Carbon filters significantly enhance the taste and smell of water by removing chlorine, chloramines, and other chemical compounds commonly used in water treatment. These substances often leave behind an unpleasant, chemical flavor. By trapping these contaminants, carbon filtration delivers cleaner, fresher-tasting water.
Removes a wide range of contaminants
Activated carbon is highly effective at capturing a broad spectrum of organic chemicals, including pesticides, herbicides, VOCs, and chlorine byproducts like trihalomethanes (THMs), all of which can pose health risks.
Environmentally friendly
Many activated carbon filters use sustainably sourced materials, such as coconut shell carbon. Coconut-based carbon is not only renewable but also often more effective due to its finer pore structure compared to traditional coal-based carbon.
No electricity required
Activated carbon filtration is a passive process. Water flows through the filter naturally, meaning there’s no need for pumps, electricity, or moving parts, making it energy-efficient and reliable even during power outages.
Versatile and widely available
Activated carbon filters come in a variety of forms to suit different needs, including pitcher filters, faucet attachments, under-sink systems, and whole-house filtration units. This makes it easy for consumers to find a solution that fits their home and budget.
Neo-Pure 10" Carbon Block Undersink Drinking Water System
Disadvantages of carbon filtrationWhile activated carbon filters are highly effective for many applications, they do have some limitations that users should be aware of.
Does not remove all types of contaminants
Activated carbon filters are highly effective at removing organic compounds, chlorine, and improving taste and odor—but they aren’t designed to eliminate everything. They do not effectively remove bacteria, arsenic, nitrates, fluoride, or certain heavy metals like mercury. However, some carbon filters include a lead-reducing additive that can significantly reduce lead levels.
To target contaminants that carbon filters miss, additional treatment methods, such as UV purification or reverse osmosis, are recommended. Most reverse osmosis systems also include a carbon filter as part of their multi-stage process.
Requires proper sizing and maintenance
Like any type of filter, the carbon filters must be sized appropriately for the water demand and replaced regularly for optimal performance. Neglecting maintenance can reduce filtration efficiency and allow contaminants to pass through.
Not ideal for hot water
Activated carbon filters are designed for cold or room-temperature water. Exposure to hot water can damage the filter media and drastically reduce its effectiveness.
Types of activated carbon filtersActivated carbon filters come in several forms, each tailored for different water filtration needs. Understanding the differences can help you choose the right type for your specific needs.
PAC (powdered activated carbon)
PAC features an extremely fine particle size, giving it a high surface area for adsorption. It's commonly used in point-of-use filters, such as faucet attachments and inline cartridges. PAC is typically derived from sources like wood, coconut shells, or coal, offering flexibility based on the desired filtration performance and sustainability goals.
GAC (granular activated carbon)
GAC consists of larger, loose carbon granules, making it a popular choice for whole-house water filtration systems. It offers fast water flow rates and effective chlorine and chemical reduction. GAC filters are available in both coal- and coconut-based versions, with coconut-based options often prized for their finer pore structure and renewability.
EAC/carbon block (extruded activated carbon)
EAC, also known as carbon block, is made by compressing powdered activated carbon together with a binding agent to form a dense, solid block. This structure forces water to spend more time in contact with the carbon, improving filtration efficiency. Carbon block filters are commonly used in under-sink or countertop filtration systems where higher contaminant removal rates are desired.
Catalytic carbon
Catalytic carbon is an advanced form of GAC or EAC that has been specially treated to enhance its reactivity. It is particularly effective at removing stubborn contaminants like chloramines—a disinfectant often used as an alternative to chlorine in municipal water supplies. Catalytic carbon also performs better against certain VOCs and other persistent chemicals compared to standard activated carbon.
Upflow Non-Electric Catalytic Carbon Filter
Coconut shell vs. coal-based carbonActivated carbon can be made from a variety of raw materials, but two of the most common are coconut shells and coal. Each type has unique properties that impact how it performs in water filtration.
Coconut shell carbon
Coconut shell-based carbon is made by processing the hard outer shells of coconuts. It has a very fine pore structure, making it especially effective at removing smaller organic compounds, chlorine, and VOCs. Coconut shell carbon is considered more environmentally friendly because it's a renewable resource and produces less ash during activation. It’s often preferred for drinking water applications because it tends to give water a cleaner, crisper taste.
Coal-based carbon
Coal-based carbon is made from bituminous or lignite coal. It has a broader range of pore sizes, which can be beneficial for removing larger organic molecules and certain industrial chemicals. While effective, coal-based carbon typically generates more waste during production and is less sustainable compared to coconut-based alternatives. It’s still widely used, especially in large-scale or industrial water treatment systems.
What contaminants do activated carbon filters remove?Activated carbon filters are best at removing chlorine, bad tastes, and foul odors, but some may be certified to remove other contaminants. Look for the NSF certification on a carbon filter to find out exactly what it can remove.
|
Contaminant |
Removed by carbon filter |
|
Chlorine |
Yes |
|
VOCs (volatile organic compounds) |
Yes |
|
Chloramines |
Yes, with catalytic carbon |
|
PFAS |
Yes, with extended contact time |
|
Pesticides and many organic chemicals |
Yes |
|
Waterborne radon |
Yes |
|
Arsenic |
No |
|
Nitrates |
No |
|
Hardness minerals |
No |
|
Bacteria |
No |
|
Heavy metals |
No, unless paired with other media (e.g., ATS, KDF) |
While activated carbon is highly effective at removing many chemicals and improving taste and odor, there are ways to enhance its performance even further.
Use a filter with a smaller pore size
Dissolved minerals like calcium and magnesium can pass through a carbon filter without being captured. However, using a carbon filter with a pore size smaller than one micron adds a mechanical filtration benefit with other materials. Filters this fine can physically block contaminants such as coliform bacteria, cysts, and other contaminants smaller than 1 micron, even though these substances don't chemically bond to the carbon.
Incorporate specialized media
Sometimes materials are added to carbon to expand its range of filtration capabilities:
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Silver-infused carbon: Adding silver creates an antimicrobial surface that helps inhibit the growth of bacteria within the filter media.
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KDF media: Some carbon filters incorporate Kinetic Degradation Fluxion (KDF) media, a blend of copper and zinc. KDF creates a chemical reaction that transforms dissolved heavy metals (ferrous form) into solid particles (ferric form), allowing them to be trapped within the carbon matrix. KDF media can be used to remove lead and iron from water.
To get the best results from your activated carbon filter and to protect your water quality, it’s important to follow a few key guidelines during installation and everyday use.
Choose the proper filter size
Proper sizing is critical for performance. A filter that’s too small for your household’s water usage will become saturated much faster, leading to poor filtration and more frequent replacements. Make sure to select a carbon filter rated for your daily water consumption and flow rate needs.
Always filter cold water only
Activated carbon is designed to treat cold or room-temperature water. Running hot water through a carbon filter can quickly degrade the carbon material, reducing its effectiveness and lifespan. Never connect a carbon filter to a hot water line.
Install before the water heater
Carbon filters should always be installed on cold water lines, before the water heater. This setup protects the filter from hot water damage and ensures that all the water entering the home is properly treated before heating.
Replace spent filters promptly
Once a carbon filter reaches its adsorption capacity, it no longer captures contaminants effectively. Even worse, it can begin to release previously trapped pollutants back into your water supply. Staying on top of filter changes is critical to maintaining safe, high-quality water.
How often do you need to change an activated carbon water filter?To maintain clean, great-tasting water, it’s important to replace your activated carbon filter every six months to one year. No matter what, a carbon filter should never be used for longer than one year, even if it still seems to be working.
If a filter is left in place too long, the carbon’s pores become saturated. Once full, the filter can't adsorb any more contaminants—and worse, previously captured particles may break free and leach back into your water supply, leaving the water dirtier than it was before filtration.
However, the exact lifespan of a carbon filter depends on several factors:
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Daily water usage: The more water you use, the faster the carbon media will become saturated.
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Incoming contaminant levels: Higher levels of chlorine, VOCs, or other pollutants will cause the carbon to reach its capacity more quickly.
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Volume and type of carbon: Filters with larger amounts of activated carbon, or those made with higher-quality materials like coconut shell carbon, typically last longer than smaller or lower-grade options.
Signs it’s time to replace your carbon filter
Because the life span of a carbon filter varies by situation, it’s important to watch for these signs that your filter is no longer functioning properly:
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Changes in taste or odor: If your water starts to taste or smell off again, it’s a strong sign the carbon can no longer effectively remove contaminants.
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Noticeable drop in water quality: Visual cloudiness or other changes in water appearance may indicate that the filter's performance is declining.
Pro tip: Your water flow won’t change when the filter goes bad. Unlike sediment filters, carbon filters don’t typically "clog" in a way that restricts flow. Instead, they gradually lose their ability to trap contaminants through adsorption, meaning your water quality worsens even if the water still flows normally.
Alternatives and additions to carbon water filtersWhile activated carbon filters are highly effective for improving taste and removing many common contaminants, they aren’t a complete solution for every water quality issue. In some cases, it’s necessary to pair carbon filtration with additional systems for comprehensive water treatment. Here are a few alternatives and additions to carbon filtration.
Sediment filters
Carbon and sediment filters perform different but complementary roles in water filtration. Sediment filters act as mechanical barriers, trapping dirt, sand, rust, and other large particles based on their micron rating, only allowing water and smaller particles to pass through.
Because carbon filters are designed for chemical removal rather than physical particle capture, they do not work effectively as sediment filters. For complete water treatment, it’s often necessary to use both types of filters: a sediment filter to remove physical debris and a carbon filter to improve taste, odor, and chemical safety.
Ceramic filters
Ceramic filters are another form of mechanical filtration, but they operate a little differently from standard sediment filters. Thanks to their extremely fine pore size, ceramic filters can block not only dirt and debris but also some microorganisms like bacteria and protozoa.
To expand their capabilities, many ceramic filters incorporate activated carbon, either blended into the ceramic material or added as a carbon core inside the filter. This combination allows a ceramic filter to provide both mechanical filtration (removing physical particles) and chemical reduction (targeting tastes, odors, and certain contaminants), offering a broader range of protection in a single system.
Reverse osmosis systems
Carbon filtration plays an important role in the reverse osmosis (RO) treatment process. Most RO systems include at least one carbon filter, and many incorporate two or even three stages of carbon filtration. However, RO systems go beyond what a simple carbon filter can do.
At the heart of an RO system is a semipermeable membrane that removes dissolved inorganic compounds, heavy metals, and radionuclides—contaminants too small for carbon to capture on its own. Carbon filters are used within the system to protect this delicate membrane by removing chlorine and other chemicals that could otherwise degrade or destroy it over time. Together, carbon filtration and reverse osmosis provide a highly thorough and effective water purification solution.
Choosing the right filtration setup for cleaner water
Activated carbon filters are a trusted choice for improving water taste, odor, and overall quality, but understanding both their limits and capabilities is key to choosing the right solution for your needs. Whether you use a carbon filter on its own or combine it with other technologies like sediment filters, ceramic filters, or reverse osmosis systems, regular maintenance and proper setup are essential for long-term performance. By following a few simple best practices, you can enjoy safer, fresher water with confidence.
Trust Fresh Water Systems with all your water filtration needs. With decades of experience in water treatment and filtration, we’ll help you find the perfect solution for your home.
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Comments
Looking at putting in a water softener system in our house with granular carbon to remove Chlorine. One is Culligan system with a replaceable Carbon filter and the other is a system where the granulated carbon and the resin are in the same tank. The carbon is on top with a screen separating them. They claim that the granular carbon can last 5-7 years before replacing and it gets “cleaned” when the system goes through its regeneration step. Have you heard of this set up?
Thanks
Mike Ewin
I have 32000 liters of alcohol with acetaldehyde concentration of 40 μL/L. I want to reduce it to below NMT 10 μL/L. Do you have any activated charcoal filters to help removing the impurity?
Does activate carbon filters work well with hot water? We want to filter water from a solar water heater storage tank. The tank is rated at 180 degrees but I don’t know if the water from the tank would reach that temperature before it passes through the filter. Thank you very much
What may happen if the carbon filter was installed in the opposite direction of the flow direction that should have been installed “This type of carbon is the one made from the shell of a coconut”.
Thanks in advance for your support.
Many thanks!
Walter
The key element to successful adsorption is contact time. If high pressure is combined with high flow rate, it is definitely a factor. After that, the concentration of the compound to be removed as well as other organic compounds will more quickly consume adsorption sites affecting capacity. In water applications, pressure alone doesn’t seem to be a performance factor in either direction (plus or minus), keeping in mind the typical pressure maximum for the carbon being used either in granular or cartridge form are more about the housing or tank in which it is used than the media itself.
Hi Gene!
Culligan has sold many water systems over the years. Compatible filters are available for most of them but not all. If you can provide us with the model number, or even a picture, we can help you find the right filter.