Beginner’s Guide to Charcoal Water Filters: Ancient Water Filtration

Did you ever wonder why we didn’t die out from contaminated water? If you think about it, some common ancestor of ours found a way to filter their drinking water. This is, of course, after some of their family and friends died. Take a look at charcoal and how it filtered water in the olden days.

What is Charcoal?

Based on studies, carbon is an extremely porous material that attracts and holds a wide range of harmful contaminants.

Charcoal is also carbon. Charcoal becomes activated when millions of tiny pores between the carbon atoms open up due to its mixture with oxygen.

Most people use special fabrication techniques to mix oxygen with charcoal and produce an even more permeable byproduct, making it more attractive to impurities and contaminated chemicals. These active or activated charcoals are very often used to adsorb odorous and colored substances from gases or liquids.

An example of gas adsorption is when charcoal is placed inside a refrigerator to remove the bad odor inside it. This is actually the very reason why some mothers put charcoal in their refrigerators at home.

In the case of water pollutant adsorption, as it passes over the positively charged carbon surface, the negative ions of the toxins are drawn to the surface of its particles.

History of Activated Charcoal

As it is written in an article in, the Egyptians and Sumerians were the very first people to produce and use charcoal as a fuel to reduce some elements in the process of manufacturing bronze.

The two civilizations also discovered that it can be used as a preservative, and thus started capitalizing on its anti-bacterial properties. They used charcoal to prevent wood from rotting especially when it is buried in the wet soils of Nile River.

As centuries passed, more and more useful applications of charcoal were discovered and exercised.

It was used to seal or block holes in ships; it was also utilized to scorch wooden barrels to preserve the water and other items stored in them.

These uses of charcoal are extensively used until today, especially in the case of water filtration, where activated charcoal is the main component.

How Does Activated Charcoal Work?

In reality, there are only two methods by which activated carbon may be able to remove pollutants from water; one is through adsorption and the other is through catalytic reduction.

‘Adsorption’ refers to the attraction of atoms, ions or molecules from a gas, liquid or dissolved solid into a surface. This is different from absorption because particles undergoing absorption are taken up by the volume and not by the surface (as in the case of adsorption).

On the other hand, catalytic reduction is a process wherein the negatively-charged ions of the contaminants are attracted to the positively-charged activated carbon.

Organic compounds are filtered by adsorption and residual disinfectants such as chlorine and chloramines are removed by catalytic reduction.

Activated carbon filters remove or may reduce the amount of hazardous organic chemicals and hundreds of man-made substances found in tap and ground water.

Although activated and catalytic carbon filters are usually effective at removing chloramine, hydrogen sulfide and heavy metals, they are not always successful in eliminating dissolved inorganic impurities or metals such as minerals, salts, copper and certain radio nuclides. To get rid of these contaminants, it is preferable to use either a reverse osmosis water filter system or a distiller.

Different Types of Carbon Filters

As of now, there are just two (2) principal forms of carbon filters utilized in the filtration industry – powdered block filters and granular activated filters.

Powdered Activated Carbon (PAC) has a relatively smaller particle size compared to Granular Activated Carbon (GAC) and consequently, presents a larger surface to volume ratio.

Usually, the former is more effective in removing a larger number of impurities than the latter.

Most carbon filters use secondary media or elements, like silver, to avoid bacteria from multiplying within the filter. Otherwise, the activated carbon itself may be drenched with silver to produce this bacteriostatic property.

PAC Powdered Block filters

According to an article in LinkedIn written by author and consultant Nikhilesh Mukherjee, powdered carbon block filters allow carbon particles to maintain their initial position relative to each other. This prohibits channeling of water which is very common with GAC filters.

There are also two important things to be considered in determining the performance of a powdered carbon block. These are:

  • particle size distribution of carbon

  • path length of water within the carbon block

These considerations are decided by the manufacturer based on the quality and quantity of water the filter can and is expected to handle and are not released.

Issues with Powdered Carbon Filters

Reducing particle sizes can very much enhance the capability of the filter to remove contaminants with similarly small particle sizes, as stated in Mukherjee’s blog. At the same time, doing this also adds resistance for water to flow through the carbon block and may cause the flow rate to drop reasonably.

Low flow rate is the most common consumer issue with powdered carbon block especially for those who use gravity filters.

Generally, PAC powdered block carbon filters are capable of providing many advantages which GAC filters, on the other hand, cannot offer.

However, both GAC and PAC carbon filters have a limited ability to remove contaminants from drinking water. Even with a powdered block filter’s properties, PAC cannot remove bacteria and virus from this kind of water, unless it is specifically designed to do so.

Hence, before using carbon filter as a standalone filter, one is required to know the contaminants present in his supply water.

GAC Filters

GAC (granulated active carbon) filters are fixed and loose bed carbon filters.

It contains an outer housing which is commonly shaped like a cylinder and carries carbon. The ratio for the filter is decided based on the velocity of water that passes through it, in order to minimize pressure drop, specifically in gravity based application.

Fluidization, nevertheless, has never been an issue with gravity filters. It is guaranteed that water velocity never reaches a point of transition between fixed bed regime and a bubbling regime in specialized high quantity filters.

Although activated carbon is a very useful adsorbent, loose carbon particles present in GAC filters might limit the full benefits that a carbon-based filter can offer.

Issues with GAC Filters

A common problematic concern with GAC filters is that, as water travels through the filter, it finds the path in the loose carbon bed where there is least resistance. Hence, during channeling process, water bypasses carbon in the filter making the adsorption capacity of carbon underutilized.

Bacterial growth in GAC filters is also a very often phenomenon. When micro-organisms are present in contaminated water and it moves through the loose GAC bed, it creates stationary pockets of contaminated water within carbon bed.

The trapped bacteria multiply immediately within the pores of GAC. These bacteria eventually find their way into the clean filtered water.

There are times when consumers still find carbon particles in filtered water during use. This is due to generation of fines produced by the wearing out of carbon particles by friction on the loose bed.

GAC filters also can’t be regenerated by washing and can’t clean turbid water.

Whole House Carbon Filter

According to a description of whole house water filter systems in, it increases clarity of an entire home’s water by removing residue deposits, which, at the same time, can also extend the lives of appliances that process water.

Advantages of Whole House Carbon-based Filters

Primarily, for a household which uses water frequently, carbon water filters should be the first choice. This is basically because it is most famous for removing traces of chlorine effectively, which if not done would otherwise result in a water with a very unpleasant taste.

As an article in suggests, this kind of water filtering system does not require electricity to work because it depends only on the pipes’ pressure. Thus, it is classified as a passive sort of filter. Naturally, this is good, since it is a great economic advantage to run a water filtering system without having to use electricity involving considerable expenses.

Another notable trait of carbon water filters is that, while they remove the dangerous contents present in water, they do not get rid of the healthy nutrients in the process. Nutrients in the water are preserved and left beneficial.

This type of water filter system is preferable because having it won’t cause a household too much trouble about maintenance issues. As a matter of fact, it requires a very small amount of maintenance which is mostly about regular cleaning and replacement of the filter element every three months or so, and that’s it.

You may also customize your carbon filters based on the substances and contaminants you are most troubled with. There is a wide range of filters to choose from and finding the one which would suit your needs won’t be a problem.

Carbon water filters may also correspond with other kinds of water filtering solutions as well, and they can be used in pairs to provide best results. Usually, they are used as a pre-filter to complement a reverse osmosis system; or added to distillers to remove traces of volatile substances.

Disadvantages of using carbon-based water filter

If the filter is stacked and remained unused for a long period of time (a month at least), bacteria will surely multiply inside it. The developed bacteria may or may not be harmful. However, it is still an undesirable situation.

If this happens, one must flush the filter for half a minute a day until assured that no more bacteria is present within it.

As mentioned earlier, certain pollutants may not always be removed when using a carbon water filter. Some of these pollutants are fluorides, nitrates, toxic minerals and a range of micro-organisms.

It is evident that the advantages of using a carbon-based water filter are far greater than its disadvantages. Consequently, installing a filtering system like this is highly recommended if one’s priority is to protect his family from toxic substances, impurities and contaminants residing in the water, while keeping expenses to a minimum. Besides, the prices of whole house carbon water filters only run from $500-$1500.


If you are wondering how to create a do-it-yourself carbon-based filter, here is a step-by-step guide lifted from

  1. Obtain fresh charcoal that has cooled completely.

  2. Crush your charcoal into small bits, from powder up to the size of aquarium gravel.

  3. Obtain or fashion a cylindrical container (taller is better than wider) with open ends.

  4. Fill the smaller opening with tightly-packed grass or a piece of fabric (if both ends are the same diameter choose either one) to prevent the charcoal from falling out or running through with the water. Or if you are using a bottle that still has its cap, poke a small hole in the cap before placing your fabric or grass.

  5. Pack the crushed charcoal into the container tightly. The idea here is to create as fine a matrix as possible for the water to drip through slowly, thus trapping more sediment. If the water runs rather than drips through the filter, you will need to pack your charcoal tighter. You should have enough crushed charcoal to fill your cylinder about halfway up.

  6. It is a good idea to place a couple of inches of packed-down grass or sand, or another piece of cloth on top of the charcoal to prevent it from becoming displaced when you add your water.

  7. Place your filter atop a container to catch your water.

  8. Slowly pour the untreated water into your filter, filling the remainder of your cylinder with water and allowing it to slowly percolate through. Remember, the water should drip slowly out the bottom of your filter.

  9. After all of the water has run through the filter, pour it back through as many times as needed to make it clear. It is usually done at least two or three times.

  10. Once the desired clarity has been achieved, bring water to a boil for a few minutes in order to make sure it is completely sterilized. Remember, boiling is the only way to ensure safety from pathogens. And that’s it. Clear water at your service!

If our ancestors could do it, then you can do it yourself. This may be a handy thing to know when the water pump breaks down, during camping trips or when there’s an emergency.

Why don’t you make this your home project this coming weekend? Tell us how it went and let’s see if you’re as good as the ancient Egyptians!


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