Post Carbon Filter Function | What Is It?

Post Carbon Filter Function

The post-carbon filter function is a filter that’s used to make your drinking water is as clean as possible. The concern of many household owners is that the water coming from the tap is still full of chemicals and various toxins. Excessive chlorine is a common concern, and various metals can still be present. That’s why we sometimes say that the water has a “metallic” taste.

There are two types of carbon filters: pre and post-carbon filters. Both can work together, and there are some differences between the two. Both of them use activated carbon granules to cleanse the water. They remove chlorine, volatile organic compounds (VOC), and remove funny tastes and odors from the water.

About Post-Carbon Filter Function

In most household systems, the water comes from a community plant that aims to clean most chemicals and toxins from the water before it comes to our household. This is true; however, many chemicals are still left, and chlorine is added.

That’s a concern for some people, as they might be allergic to chlorine. Additionally, the water might taste weird, and it might have some sort of a metallic taste.

That’s why many households utilize RO (reverse osmosis) systems to make sure the water is as clean as possible. And these RO systems have various types of filters. One of the most common types of filters is activated carbon filters. To understand the post-carbon filter function, let’s take a closer look at a typical RO system and how it works.

RO Systems

Many households nowadays utilize a reverse osmosis system that will additionally cleanse and purify the water coming from the communal water treatment plant. It uses a permeable membrane and a number of various filters to do that.

  • First, the water passes through a sediment filter. That’s where larger particles are removed, such as rust and calcium carbonate.
  • Some RO systems will have a second sediment filter that will remove even the smaller sediment particles that are left by the first sediment filter.
  • Then comes an activated carbon pre-filter that will trap chemicals and smaller particles, such as chlorine. It’s a crucial step of the RO system; these filters are usually larger than post-carbon filters because they cover the source water and have to handle much more water at once.
  • At the heart of the RO system is the reverse osmosis filter. It is a thin composite membrane that traps all the particles and unwanted chemicals, which is where most of the debris gets covered.
  • Then comes the post-carbon filter function. This is the filter we’ll be talking about in this article. It’s an optional filter, but most of the RO systems already have this filter installed. Additionally, many users choose to install this filter themselves. Its role is to remove the toxins and particles that were left by the first activated carbon filter and remove the odors. It will be smaller than the first filter, as it will cover 30-35% of the water load that the first one has to.
  • Some RO systems also utilize an ultraviolet lamp that will remove bacteria and microbes, thus preventing any possible infections and diseases.

Reverse osmosis filters will effectively make the drinking water much cleaner. They have various filters and a membrane that trap particles of up to 0.001 micrometers in size. They can be extremely helpful for making seawater drinkable, for example, as they remove salts and other particles that make seawater non-drinkable.

The Post-Carbon Filter Function

As we can see, the role of a post-carbon filter function is to provide an additional layer of protection and to clean the water that passes through the system. They have several benefits, and they are an optional feature. But many people opt to have them included because they are so effective. In most cases, you will have to purchase the filter separately and install it manually. However, there are many systems that already come with the filter included.

So what are the main roles of the post-carbon filter function?

  • They are used for clarifying the liquids that pass through it.
  • They get rid of the peculiar smells and odors and get rid of the taste.
  • Remove the organic solvents that color the water, which makes the water colorless.
  • Remove chlorine, chemicals left by the other filters, and smaller particles.
  • Effective for alcohol purification and to make alcohol drinks cleaner.

A post-carbon filter will have small granules of activated carbon, which can be either coconut activated carbon or other types. These granules are usually much smaller than in the pre-filter, as they will handle much less water, but will also be slightly more precise and delicate. The working temperature of a carbon filter like this is usually at about 40 degrees Celsius or lower (104 degrees Fahrenheit or lower).

How Does an Activated Carbon Filter Work?

Activated carbon, or activated charcoal, is a type of charcoal that has smaller pores that increase the surface area that it impacts. It’s produced by burning the source material (wood or other sources) at very high temperatures with a limited supply of oxygen.

This makes the charcoal more porous, and it creates smaller fractures within the charcoal. These fractures will stay compact and will play a crucial role when they’re in a filter.

The carbon is then transformed into smaller granules, which are then a part of the filter. These granules trap pollutants with adsorption, which is a process where the particles get stuck to these pores within the activated carbon granules. This implication is a crucial part of the water treatment module that’s presented in RO systems.

Activated carbon can trap various particles with adsorption, such as chemicals, smaller debris, and of course, they also trap odors and remove tastes.

As the granules trap these particles, they also become slowly, but surely, overloaded, and will need to be replaced after some time. How often depends on the load and the number of granules a filter has.

With post-carbon filters, this might mean replacing the filter from time to time; usually, they will last a couple of months before they need replacement. This will present an additional cost, but luckily. We’re getting the purest level of water out of it.

Activated carbon is also present in many other types of filters:

  • Air purification filters.
  • Industrial use.
  • Medical purification for overdoses, for example.
  • In chemistry.
  • For removing volatile organic compounds.
  • In agriculture.
  • For distilled beverages (alcohol)
  • Gas purification.

You can see just how useful these types of filters are. And they are also useful for water purification, of course.

Pre-Carbon Filter vs. Post-Carbon Filter Function

So we’ve already established that an RO system can have two activated carbon filters: the pre-filter and the post-filter. But what are the differences between the two of them?

The main principle stays the same: they both use activated carbon to remove particles and odors from the water. The first, pre-filter, will remove most chemicals, particles, and trap odors at the same time. Then the water will go through the osmosis membrane.

But after that, there might still be chlorine left, especially if the pre-filter is not as effective anymore. This is where the post-carbon filter function comes into play.


The main difference between the pre and the post-filter is the size. The pre-filter will have to handle much bigger loads of water, as it will use the water straight from the source in most cases. Meanwhile, the post-filter will only have to cleanse the permeate that goes through the osmosis membrane beforehand. This means about 30-35% of the source water.

That’s a big difference, so it’s to be expected that the post-filter will be smaller.

Granule Size

While the pre-filter manages much higher flows of water, they will also have to cover more surface area. This means that the particles, or the granules of activated carbon, will be significantly larger in pre-filters than in post-filters. That’s the case in most filters, although it’s not always true.

There will also be much less activated carbon in post-filters – there might be up to 100 grams of activated carbon granules in post-filters, while pre-filters will have 280 grams or even more.

Choosing the Post-Filter

When it comes to choosing the post-filter, you’ll have to consider a couple of things. First, you’ll have to know what size of the filter will suit your RO system. Then, you’ll want to buy the right filter for your needs. And of course, some filters will be better than others, which means spending more, and you can also expect them to last longer.

No products found.

Most cartridges are similar, though, and the differences are pretty minimal. The biggest factor when choosing the right type is the type of RO system you have. Some are portable, while others are desktop RO systems.

Wrapping Up

The post-carbon filter function is one of the last filtering defenses of an RO system. It cleanses the water of chlorine and makes it taste better by removing the smells and odors. It’s an optional part of the RO system that can massively improve the quality of your drinking water.

Recent Posts

Post Carbon Filter Function | What Is It?