A carbon water filter is a type of filter that traps contaminants using a process known as adsorption.
Carbon filters are found in a variety of filter types, including water pitcher filters, water bottle filters, under-sink filters, whole-house filters, faucet filters, and countertop filters.
There are several types of activated carbon filters. The most popular kinds are carbon block filters and granular activated carbon (GAC) filters.
In this guide, we’ve shared a list of the most common contaminants removed by carbon water filters. We’ve also shared what activated carbon water filters CAN’T remove.
📌 Key Takeaways:
- Activated carbon filters can remove chlorine, pesticides, herbicides, some VOCs, some disinfection byproducts and other organic chemicals from tap water.
- Most carbon filters CAN’T remove microorganisms, chloramine, hardness minerals, salts, fluoride, or most heavy metals.
- Carbon block filters have a larger surface area and a slower flow rate than granular activated carbon filters, which makes them slightly more effective at removing contaminants.
- Factors affecting the activated carbon filtration process are the filter type, the filter size and surface area, the filter quality, other media used in the filter, and the flow rate of water through the filter.
Table of Contents
⚗️ What Can A Carbon Water Filter Remove?
Some of the contaminants that are reduced or removed by an activated carbon water filter are:
Chlorine is the contaminant that’s most commonly removed by activated carbon filters.
Water in the US is almost always disinfected with chlorine. This chemical is needed to kill bacteria and viruses in water and make it potable (safe to drink), but it gives water an unpleasant swimming pool taste and odor.
Premium activated carbon filters can reduce at least 90% free chlorine, as well as the unpleasant tastes and odors associated with chlorine in water.
📌 Good to know: Some US states use chloramine disinfection. Unfortunately, a standard activated carbon water filter can’t reduce this chemical. You’ll need to buy an enhanced carbon water filter, known as a catalytic carbon water filter, to filter out chloramine.
Small amounts of chlorine aren’t thought to be harmful, but they produce harmful byproducts that are dangerous to human health.
Activated carbon has proven effective in reducing chlorine byproducts with halogen elements (such as chlorine, iodine, and bromine). In fact, a study found that carbon filters are the most effective point-of-use filters for reducing adsorbable organic halogens, offering up to 94% removal.
Activated carbon filters have shown promise in reducing an emerging contaminant in our drinking water supplies: pharmaceuticals.
Pharmaceuticals are natural or synthetic chemicals that get into our water through human waste and improper disposal of medications (such as flushing drugs down toilets or sinks). In small amounts, they’re not thought to have health effects, but they’re dangerous to aquatic life.
A study found that activated carbon can remove many pharmaceutical residues in wastewater treatment, and may be a good alternative treatment to ozone.
Volatile organic compounds (VOCs for short) are organic chemicals that get into drinking water through industrial dumping, improper disposal of household products, and leaks and spills.
There are hundreds of VOCs. Activated carbon filters can’t remove all of them, but they target some of the most common VOCs, including formaldehyde, benzene, tetrachloroethylene, and methylene chloride.
PFAS are a type of synthetic compound that were once used heavily in the manufacturing industry to make firefighting foam, waterproof materials, non-stick cookware, and more.
These chemicals are known as “forever chemicals” because they linger in the environment for centuries, and are nearly impossible to break down. Some of the known health effects of PFOS are cancer and liver damage.
A study found that activated carbon filters can reduce about 73% of PFAS contaminants in drinking water.
Pesticides are chemical substances used to control pests in agriculture or public health protection programs. Due to their widespread use, pesticides leach into surface water and groundwater supplies through soil seepage and surface water runoff.
There are tens of pesticides, and most activated carbon filters can remove a handful of the most common pesticides that exist in the environment today, including lindane, chlordecone, kepone, heptachlor, and chlordane.
Herbicides are often used hand-in-hand with pesticides to control weeds and increase the production of desired crops in agriculture. Again, these chemicals can often end up in local water supplies, due to poor or uncontrolled farming practices.
Activated carbon can reduce several common herbicides in tap water, including glyphosate (Roundup), atrazine and 2,4-D weedkiller.
Phosphate, a chemical containing the mineral phosphorous, is used in fertilizer and feed in agriculture, as well as construction, personal hygiene, and food products. Runoff, improper industrial waste disposal, and sewage all leach phosphate into the environment.
Activated carbon is considered relatively effective at reducing phosphate in water, with a maximum phosphate removal of just over 50% (according to a 2016 study).
Lithium is a metal that occurs naturally in soils and rocks, which is usually how it ends up in our drinking water. At the moment, the potential health effects of lithium in drinking water are largely unknown.
Active carbon filters made from charcoal can remove around 90% of lithium in water.
🚫 What a Carbon Water Filter CAN’T Remove
There are thousands of trace contaminants in most drinking water sources. Carbon filters can only reduce or remove a handful of these.
Some of the contaminants that CAN’T be removed by an activated carbon filter are:
Activated carbon filters can’t reduce fluoride in drinking water.
If you want to remove fluoride from your water, buy an activated alumina filter or a reverse osmosis system.
A standard activated carbon filter can’t reduce chloramine.
The best type of chloramine removal filter is an activated catalytic carbon filter – which is activated carbon with an advanced capacity, allowing for the removal of a greater number of contaminants.
Minerals And Salts
Minerals and salts are retained in water filtered by activated carbon. Most people prefer to keep healthy minerals in their drinking water, so this isn’t necessarily a bad thing.
If you want to drink water that’s completely free from minerals and salts, you’ll need to buy a reverse osmosis filter.
Calcium and magnesium minerals contribute to water hardness. A carbon water filter can’t remove these minerals.
To treat water hardness, you’ll need to install a whole-home water softener or salt-free water conditioner.
Most Heavy Metals
Most heavy metals aren’t attracted to carbon media, so they’re retained during the carbon filtration process.
Only special activated carbon filters can reduce heavy metals in water. Look for a carbon water filter combined with KDF media, which reduces water-soluble metals like copper, zinc, iron, and cadmium.
Microorganisms like bacteria and viruses are small enough to slip through the pores of an activated carbon water filter.
A ceramic filter combined with carbon media is usually capable of reducing microorganisms AND treating tastes and odors.
📤 How Do Carbon Filters Remove Contaminants From Water?
Activated carbon filters use a process called adsorption to reduce contaminants in tap water.
The activated carbon water filter media has a sponge-like ability to adsorb chemicals, tastes, and smells. Carbon filters have a large surface area, enabling them to trap a large number of contaminants.
💡 How does the adsorption process work?
The dissolved impurities in water are attracted to the carbon media, and stick to its surface. Water particles pass through the filter pores, while the contaminants are left in the media.
Eventually, the carbon media becomes completely saturated with contaminants, clogging its pores and reducing its flow rate. When this happens, the filter must be replaced.
📝 What Affects a Carbon Filter’s Contaminant Removal Ability?
The below factors affect an activated carbon filter’s ability to remove contaminants from tap water:
The Filter Size & Surface Area
The larger the filter, and the bigger the filter’s surface area, the more contaminants are removed from water.
Why? Because a large filter surface area gives more contact time between water and the media, allowing more opportunity for greater contaminant removal.
The Type of Carbon Filter
As we mentioned at the beginning of this guide, there are several types of activated carbon filters. While all types of carbon water filters generally remove the same contaminants, some are more effective at contaminant removal than others.
A granular activated carbon (GAC) filter is made from loose carbon particles, while carbon block filters use fine carbon granules that are bound together into blocks, making them unable to move.
📌 Granular activated carbon filters aren’t quite as thorough at removing contaminants as carbon block filters. This is because the large surface area design of carbon block filters allows for a longer contact time with water and prevents most contaminants from passing through.
Carbon filters can also be found in point of entry (POE) and point of use (POU) filter applications. You’re most likely to find carbon block filters in smaller point of use models, such as in water pitchers and faucet filters. GAC filters, usually made from coconut shell activated carbon, offer a faster flow rate, so they’re more commonly found in larger, POE models for whole home use.
The Filter Flow Rate
The flow rate of water passing through the filter media also affects its contaminant removal ability.
For instance, a water filter pitcher uses gravity filtration, which means that water flows through the filter much slower than in an under-sink filter, which uses water pressure to send water quickly through the media.
A slower water flow allows a longer contact time between the water and the activated carbon media, giving more time for contaminants to be removed.
Other Combined Media
Often, manufacturers combine activated carbon filter media with other types of media, such as KDF, ion exchange, ceramic, or activated alumina media.
The obvious benefit of this is that the filter can remove more than just a handful of contaminants – it may also be able to remove microorganisms, heavy metals, and chloramine, depending on the filter media used.
The more complex the filter, and the more media blends used, the more contaminants can be removed.
The Filter Brand
Some filter brands are simply better than others when it comes to contaminant removal.
The better quality the filter, the more capable of contaminant removal it’ll be. Some filter designs are lacking compared to their competitors, and this is seen in their poorer filtration abilities.
📌 Look for activated carbon filters that have been tested or certified to NSF Standards – especially NSF 42, for the reduction of chlorine, taste, and odor. A carbon water filter should be able to reduce at least 90% of chlorine from water.
🤔 Is A Carbon Filter Right For You?
In our opinion, an activated carbon water filter is the right choice for you if your main water quality issue is chlorine. Carbon filters are great for people with small budgets who predominantly want to improve the taste and smell of their water by removing a handful of unpleasant contaminants.
Carbon filtration isn’t a good solution for well water. People looking to achieve thoroughly purified water shouldn’t buy a carbon filter. If you’re not prepared to spend money on new filters (usually every 2-9 months, depending on the filter size), carbon filters aren’t right for you.
If you don’t already know what your water contains, buy a home water quality test. If the test shows that your water mainly contains organic contaminants, carbon filters are a good choice.
Consider buying a filter that combines carbon media with other filter media for more thorough contaminant removal.
Read Our Reviews: The best carbon water filters for various applications
❔ What Do Carbon Filters Remove? FAQ
Do carbon filters remove hard water?
No, carbon filters don’t remove hard water. No water filter can effectively soften your drinking water. The best way to remove calcium and magnesium hard water minerals is to install a water softener, which exchanges these hardness minerals with sodium or potassium, pulling them out of the water.
Do carbon filters remove toxins?
Carbon filters remove some toxins, including chemicals and VOCs, from water. However, they don’t produce 100% toxin-free water. The only way to remove all toxins from your water is with a reverse osmosis system or a water distiller.
Does a carbon water filter remove bacteria?
No, a carbon water filter alone can’t remove bacteria. The pores of a carbon filter are large enough to allow tiny bacteria particles to slip through. If you want to remove bacteria, look at a carbon and ceramic combined filter, since ceramic filters usually remove microorganisms.
What are the benefits of a carbon filter?
Some of the benefits of a carbon filter are improved water taste and smell, harmful contaminants removed, healthy minerals retained, and affordable upfront cost and maintenance.
Is carbon filtered water good for you?
Yes, carbon filtered water is good for you because it contains a much-reduced amount of chlorine, VOCs, and other organic chemicals compared to normal tap water. Plus, it still contains healthy minerals like calcium and magnesium. With that said, carbon filtration doesn’t remove everything from water, so water from a carbon filter will still likely contain some trace contaminants.