A Guide to Carbon Block Water Filters | Water Filtration

A Guide to Carbon Block Water Filters | Water Filtration

Have you been shopping around for the right filter for your drinking water? In this article, we’ll spotlight one popular water filtration solution: carbon block filters. We’ll discuss what these filters are, what they do, and how they stack up against other water filters.

What is an Activated Carbon Water Filter? 

Activated carbon is a highly porous material that has a microscopic graphite lattice structure. When drinking water passes through this type of filter, a process called adsorption happens. During adsorption, molecules of contaminants are attracted to the molecular structure and large surface area of the carbon. In scientific terms, the positive ionic charges in the carbon attract the negative ionic charges of contaminant particles. These contaminant molecules bond with the carbon, and clean drinking water flows through the other side of the filter and into your pitcher. The filter also physically removes sediment and other larger contaminants.

Because activated carbon is highly effective and relatively inexpensive, it is a very popular filter type on the market today. One of the additional benefits of this process of filtration is that healthy minerals remain in your water, so you’ll get the most out of every sip.

What is a Carbon Block Water Filter?

A solid carbon block water filter is just that, a block of finely ground and compressed carbon that water passes through during filtration. A carbon block filter acts like a magnet; microscopic contaminants like PFAS are filtered out while clean water passes through. These carbon filters can be used in combination with other technologies like reverse osmosis, or used on their own. 

Water filtration using a carbon block may seem like a straightforward process, but there are actually several ways to do it, including: 

  • mechanical filtration
  • electrokinetic adsorption
  • physical adsorption

The mechanical filtration process is all about particle size. Think of it like a strainer: small water particles pass through while larger contaminant particles get held back. Electrokinetic adsorption is more technical. As water passes through the outside layer of the filter, this layer acquires a positive ionic charge, thus attracting negatively-charged contaminant molecules. The carbon block itself, in conjunction with physical molecular binders, can also attract particles of different sizes from your drinking water. This process is known as physical adsorption. 

What are the types of Carbon Block Filters?

The two most common types of carbon block filters are compressed and extruded. Both carbon filter types are actually a mix of carbon, mixed media, and a binding element. The difference is in how these filters are created. Compressed carbon block filters are constructed individually at high heats using a mold. Extruded carbon block filters are heated, die-cast, extruded (hence the name), and cut to size.  

Carbon compression is the more labor-intensive of the two processes, and not surprisingly, yields the higher quality results. Because of the high heat involved, highly porous binding agents are used to make compressed carbon block filters, making them ideal water filters. Compressed carbon block filters are also more expensive. Whether you choose a compressed or extruded carbon block filter, you’re making a great investment in healthy drinking water. 

Carbon Block Filters vs. Other Carbon Filters

Zooming out a bit, let’s compare two different types of activated carbon water filters. Among these carbon water filters, there are two common types: carbon block, and granular activated carbon (GAC). Let’s dig into the differences and examine which may be better for you. 

What is a Granular Activated Carbon (GAC) Water Filter? 

Similar to carbon block filters in function but different in form and features, GAC filters use a bed of granulated carbon to remove impurities. Carbon particles are bigger than .30 mm and smaller than .84 mm in GAC filters. 

A GAC water filter uses carbon to remove some bad odors, tastes, and sediment from tap water with high efficiency. When it comes to contaminants like chlorine, GAC filters get the job done. These carbon filters are particularly good at removing organic chemicals from drinking water. 

All GAC filters use carbon, but the carbon may come from different sources depending on the filter. GAC filters use a variety of media, including coconut shells, coal, and wood, to filter water. Incidentally, carbon block filters can be constructed using any of these materials as well. 

Coconut shells are particularly popular because they have 50% more micropores than other options, leading to a greater surface area and more adsorption. Coconuts are also considered a more renewable carbon source than other carbon sources, and coconut shell carbon provides a more consistent water filtration experience.

What do GAC Water Filters Remove?

Just like carbon block, GAC filters can remove large swaths of organic and inorganic contaminants.

These GAC filters work well, but must be changed regularly to avoid channeling. Channeling is when the ionic reaction between the carbon and the water passing through is reduced, leading to a lack of filtration. Basically, the water takes the path of least resistance through the carbon filter, evading the most effective water filtration particles. 

Carbon Block Filters vs. GAC Carbon Filters

Both block and GAC filters use ground up carbon to filter water, but names can be a little misleading. Ironically, granular carbon particles are actually bigger than those in carbon blocks. The particles in carbon block filters are much finer (about .045 mm to .18 mm). As a result, carbon block filters have been proven to provide 7 to 10 times more surface area than GAC filters. Consequently, carbon blocks have a greater surface area. More surface area means more available space for absorption and more effective water filtration.

You must also consider the structure of the two filters to understand why carbon block filters are more efficient at filtration. For GAC filters, the activated carbon granules are loaded in a loose bed inside the filter cartridge. Water flows through by taking the path of least resistance. In a carbon block system, the filter cartridge forces the water through the entirety of the block. With its fixed particles and lack of loose structure, a carbon block is engineered to perform consistently, making it the better choice for filter purists (pun intended). 

Two other considerations that differentiate carbon block filters and GAC filters are carbon discharge and bacterial growth. If you’ve ever used a carbon water filter and seen a black discharge on first use, chances are it was a GAC filter. With carbon block filters, manufacturers can minimize the pore size of the filter so drastically that discharge is imperceptible.

Initial discharge and some bacterial growth are both considerations, but at the end of the day, which carbon filter is more effective in your water system, carbon block or GAC? Carbon block filters are more efficient than GAC filters on average and all in all make the better choice. But you must also consider the lifespan of the filter. Carbon filters often last longer than GAC. Because the granules are finer, a carbon block filter also has a lower flow rate. 

Carbon Block Filter vs. Reverse Osmosis 

Unlike carbon, reverse osmosis water systems uses pressure and a semi-permeable membrane to remove contaminants from water. According to the CDC, “reverse osmosis systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E.coli).” RO systems can also eliminate viruses, and common chemical contaminants. Let’s consider how these commonly used filters stack up against carbon block water filters.

One downside to reverse osmosis water filters is the loss of healthy minerals. Mineral molecules are larger than water molecules, so reverse osmosis usually removes healthy minerals like magnesium and potassium from your water. When it comes to water filtration, it is possible to have too much of a good thing.

Nevertheless, both filtering methods seem effective (and are sometimes used in conjunction with one another), so which one is better? Some of the advantages of carbon block filters are size and limited maintenance. Water systems that use reverse osmosis can be costly and large. Because of this, you’ll spend less on maintenance over time with a carbon block filter. This makes carbon block the best choice for many homeowners. 

Carbon Block Filters vs. Bottled Water

Some households skip all filtration options and purchase bottled water instead. Interestingly, the Environmental Protection Agency (EPA) sets standards for tap water, while the Food and Drug Administration (FDA) regulates bottled water. Legally, FDA bottled water standards must be as high or higher than EPA tap water standards. Bottled water is definitely a safe bet when it comes to purity, but is it the best choice for your family's drinking water long term? 

While there is some debate about whether bottled water or filtered water is healthier, there can be no doubt that a filtered solution is more cost-effective. Bottled water costs add up over time, and plastic packaging used for this type of water is bad for the environment.   

Do Carbon Water Filters Work?

Filtering water using carbon has been a common practice since the days of the Ancient Egyptians. There is a reason modern charcoal and carbon water filters are so popular: they are designed using rigorous testing procedures to ensure they get the job done. Some of carbon filter design parameters include: 

  • Raw Material Selection
  • Filter Performance Objectives
  • Performance Validation
  • Filter Dimensions and Finish

The result is a reliable method for removing contaminants from your water. You’ll taste the difference in every glass for fresh, clean water. 

This is what a carbon block filter can do.

Watch Aquagear remove tap water chlorine.

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Aquagear: The Best Water Filter For Your Home

Aquagear is the best solid carbon block water filter to remove contaminants including lead, microplastics, chlorine, aluminum, pesticides, PFOS and PFOS, cadmium, and more. Our filters remove harmful chemicals while retaining the healthy minerals like potassium and magnesium that your body needs. Our filters are high-capacity and can handle up to 120 gallons of water, 3 times more than the competition, before requiring replacement. Get Aquagear today and taste the difference!


Are carbon block water filters safe?

Carbon block water filters are a safe way to filter your drinking water. 

The best carbon block water filter is tested by a third party to ensure it is safe and efficient. Aquagear is third-party tested to the highest standards to remove lead, VOCs, PFAS, microplastics, and more.

How long do carbon block water filters last?

Carbon block water filters should last between 2 to 6 months before needing to be changed, depending on the make and model. After this time, the filter will cease to effectively filter your water.

Is Brita a carbon block filter?

The Brita water filter pitcher is a coconut-based carbon activated filter. This is a true Granular Activated Carbon (GAC) filter, using carbon sand to filter out contaminants from drinking water. While GAC filters are effective, there are different types of carbon filters that are more effective. Carbon block filters can be more porous and are sometimes proven to filter out more contaminants over time. 

Do carbon filters grow bacteria?

Carbon block filters do not grow a significant amount of bacteria. According to a study conducted by the International Journal of Hygiene and Environmental Health, carbon block filters pose no significant microbial risk for users. The loose bed of carbon used in GAC filters, however, can provide enough space for bacteria to grow.