Carbon Filters for Water Filtration

Carbon filters remove contaminants in drinking water

What are Carbon Filters For Water Filtration?

Carbon filters are used in various water filtration systems to remove contaminants from drinking water. These filters are commonly found in backpacking water filters, refrigerator filters, shower filters, pitcher filters, and RO drinking water systems. Carbon is an effective medium for filtering contaminants, making it a popular choice in many filtration scenarios.

How do Carbon Filters Work?

Carbon filters remove contaminants through adsorption, where contaminants are attracted to the surface of the activated carbon and held there (much the same way a magnet attracts and holds iron filings). They also act as a catalyst to change the chemical composition of some contaminants. Activated carbon is ideal for removing chlorine, organic chemicals such as pesticides, THMs like chloroform, and many VOCs (Volatile Organic Chemicals).

Contaminants are attracted to activated carbon surface through adsorption

What do Carbon Filters Remove?

Carbon filters can effectively remove or reduce many contaminants from water including:

- Volatile Organic Compounds (VOCs)
- Chlorine
- Lead
- Fluoride
- Pesticides
- Nitrates
- Pharmaceuticals

For a more comprehensive list, read What Do Carbon Filters Remove.

How are Carbon Filters Made?

Carbon filters for water filtration are produced by grinding up a carbon scouce. This carbon source could be:

bituminous coal
peat
coconut shells

Of the above-mentioned carbon sources, coconut shells are the most widely used and are highly renewable.

To create the filter, material is heated in the absence of oxygen to 1000 degrees to bake off impurities. The material is then subjected to 1600-degree steam to “activate” the carbon. The steam leaves carbon granules filled with cracks and pores, enabling them to store large amounts of chemicals and contaminants.

Omnipure Omnipure OMB934-5m 10-inch 5 Micron Carbon Block Replacement Filter OMB934-5m

Top-Selling Carbon Block

Filter removes sediment, rust and dirt particles to a 5 micron level AND removes chlorine to improve taste and odor of water.

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

GAC stands for "granular activated carbon" and is made of tiny, loose granules of carbon. GAC filters are usually used as a "polishing filter' in the water filtration process and are highly effective at improving the taste and odor of drinking water.

While a GAC carbon filter is simply loose pieces of carbon, a carbon block filter is where the loose pieces of carbon are compressed together to form a filter.

Omnipure Omnipure 2 x 10 Inline GAC T33 Carbon Filter K2533 K2533

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What do GAC Filters Remove?

Granular activated carbon (otherwise known as GAC) filters have extremely high adsorption capabilities and can remove a wide variety of contaminants (see contaminant list here).

GAC filters are often used to remove VOCs, pesticides, nitrates, hydrogen sulfide, and much more.

Municipal water treatment plants use disinfectants such as chlorine and chloramine which can leave an objectional taste and odor in drinking water. GAC filters are able improve taste and odor and are therefore commonly used as one or two stages in a reverse osmosis system.

What is a Carbon Block Filter?

A carbon block filter is where the loose pieces of carbon are compressed together to form a filter.

In a carbon block filter, one pound of compressed activated carbon (the amount in a standard ten-inch filter cartridge) has the equivalent surface area of a 160 acre farm, making it one of the most absorbent materials known to man.

Because of the compressed nature of a carbon block filter, water flow rates are lower than that of a GAC filter made of loose medium. And flow rates are impacted by the micron rating of the filter. A carbon block filter is rated to a certain micron rating depending on how much the carbon is compressed. The smaller the micron rating, the finer the filtration and the lower the flow rate.

GAC vs. Carbon Block Filters

	GAC (Granular Activated Carbon)	Carbon Block
Appearance
Medium Type	Loose carbon granules	Compressed carbon
Filtration Purpose	Improves taste and odor	Removes small contaminants
Typical Use	To improve taste and odor of water by removing chlorine, hydrogen sulfide (rotten egg odor), etc.	Can filter sediment, as well as pesticides, heavy metals, and other contaminants
Flow Rates	Generally higher flow rates	Generally lower flow rates
How Often to Replace	Every 6-12 months*	Every 6-12 months*
Advantages	May do a better job at adsorbing certain contaminants	Can adsorb AND filter

*Filter change schedule may vary based on local water conditions and household usage.

Carbon Block Filters vs. Granulated Carbon Filters

What is the difference between a carbon block filter and a GAC filter? Carbon block filters and GAC filters are made of the same material, but one is made of ground up loose carbon and the other is the loose carbon that has been compressed.

Many water filter systems use both carbon block AND GAC filters in the water filtration process.

Carbon block filters are made of a solid block of compressed carbon and are often used as a pre-filter in reverse osmosis and other water filtration systems. Carbon block water filters are extremely effective in filtering out a variety of contaminants including very small contaminants or particle size. Water will often flow slower during this filtration stage due to the compact nature of the compressed carbon.

The granular activated carbon or GAC water filter is made of loose carbon granules. Water flows more freely through this stage, so flow rates are higher for GAC filters than carbon block filters. GAC filters also have very high adsorption properties and can remove contaminants including chlorine, hydrogen sulfide, lead and much more.

What is a Catalytic Carbon Filters?

Catalytic carbon filters contain a special catalytic carbon block and are highly effective at reducing chlorine and chloramine.

Carbon Block Filters are Rated in Microns

Carbon block filters are rated by the size of contaminants that can be removed at the micron level. Generally, the range is from 50 microns down to .5 microns. The higher the rating, the larger the contaminant size. Very small contaminants will need to be filtered with a small micron size rated filter, such as .5-micron rating.

micron filter size for understanding water filter micron rating

Reverse Osmosis Filter Change Schedule


Sediment Filter	Carbon Filter	RO Membrane	GAC Polishing
Change out every 6-12 months	Change out every 6-12 months	Change out every 24 months	Change out every 6-12 months

*Filter change schedule may vary based on local water conditions and household usage

How Often Should Carbon Filters Be Changed?

For reverse osmosis drinking water systems, both the carbon filter and the polishing filter should be replaced every 6-12 months. The lifespan of a carbon filter can vary based on quality of water and usage.

FAQs

Are Carbon Filters Safe?

Yes. In fact, many of the carbon filters we carry have been tested and rated by a third party for material safety.

Do Charcoal Water Filters Work?

Charcoal is a type of carbon that was used in the past, but rarely used now. Typically, all carbon filters are now made from coconut. Usually when someone refers to "charcoal filters", they mean carbon filters, and carbon filters are extremely effective in removing contaminants from water.

What are Coconut Water Filters?

Coconut water filters are made of coconut husk carbon that has been vacuum heated in a lab and cleaned. Coconut is the most common type of carbon used in water filters today as they are effective at removing bad tastes, odors, VOCs, chlorine, pesticides, and more.

What are Catalytic Carbon Filters?

Catalytic carbon filters are a type of carbon filter that contains a special catalytic carbon block. Catalytic carbon filters are highly effective at chlorine and chloramine reduction.

What do Carbon Filters Remove from Water?

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