How Do Water Filters Work?

Take a look at a glass of water; you would presume it to be safe to drink. But the fact is that the cleanest appearing drinking water can have particles that cannot be seen with the naked eyes. More than often, small dissolved minerals are present in water which may alter the taste, though are harmless. However, in some cases these particles can also be microscopic protozoa or bacteria that can prove fatal. These contaminants are a daily struggle for almost 700 million people in the world.

Not to worry! After the invention of the water filters, it has become easy to keep the bacteria and other nasty buggers out of the bodies. Water filters have bought a complete change in the way we consume water. They help eliminate impurities from water by providing a fine physical barrier. The process incorporates passing of water through a granular bed made of san at a very low speed. In this way, the media holds back the solid matters, allowing the clean water to pass down.

How Water Filters Work: The Process

Bartholomew  Photography

Bartholomew Photography

Filters contain substances which absorb and trap the minerals and pollutants flowing in the water. Now this substance is referred as the medium. There are a lot of kinds of filter media available these days. While a lot of filters mechanically trap or modify pollutants with strainer, there are other filters which make use of a process known as absorption. In this process the pollutants get retained in tiny pores of the medium itself.

So when shopping for a water filter, you must check its rating to know what size particles that it is capable of removing. All the filters get rated in microns. 1 micron is about one millionth of a metre. Even the filter ratings are segregated into two categories: nominal and absolute.

  • A nominal rating suggests the size of the smallest particle that would be removed by the filter, as per the design. It is not an accurate value though, but an estimated value. Let’s say a 5 Micron nominal filter will be able to absorb 95% of pollutants that are of size 5 microns or larger.
  • And an absolute rating filter is known for reducing pollutants by 99.9%. so if you use a 5 micron absolute filter then it will be able to reduce impurities in the water by 99.9% of particles having diameter of 5 microns or more.

Now there are a number of different styles in which water filtration can be done, in order to remove impurities and unwanted substances from water. The main filtration styles are as follows:

1. Activated Carbon Filters

One of the most common types of filters used in every home and refrigerators these days is activated carbon filter. Also called as active carbon or AC, these filters need replacement after every six months. These filters are quite effective in eliminating pollutants and bacteria that leaves a slight color, bad odor or even taste in water. Activated carbon filters are quite good at reducing the level of industrial waste, chlorine by-products and even pesticides.

AC filters can be made from a number of organic materials including wood, coal, or lignite. These filters come in numerous shapes and sizes and they have great filtration capacity. Activated carbon is the prime constituent of these filters. And since these filters have quite a huge, porous surface area, they are able to trap high amount of impurities. And when the water gets passed through different layers of the medium, all the impurities and pollutants are screened out, as per the overall rating of water filter. However, after some months, the surface of these filters can get clogged with pollutants, thus deterring the effectiveness and even barring the water flow. You can notice the filter taking long time to fill just a glass of water.

2.Reverse Osmosis

iSpring Reverse Osmosis System RCC7 ReviewOsmosis is a process in which a semi-permeable membrane easily separates two different solutions having varying concentrations. However, in case of reverse osmosis, purification is done by applying pressure to the water against the semi-permeable membrane such that single water molecules can easily pass through the medium, thus removing the contaminants. In this case, the membrane is like a mechanical filter that removes asbestos, micro-organisms, and all heavy organic compounds.

Best Reverse Osmosis Water Filter System comprises of primary four filters- sediment filter, carbon block, activated carbon block, a membrane, as well as a storage tank. This helps remove all the cholrine by-products which might still be present in water. So these filters are able to remove a wide range of impurities, utilizing just one factor and that is water pressure. This process can remove sediments, toxic substances, herbicides, pesticides, and turbidity. There are a lot of health benefits attached to the use of RO purifiers.

Other than these basic filter styles, there are some more methods used for filtration of water, which includes Distillation and Ultraviolet Light.


It is a process in which heat is applied to water so that it turns into vapors. This steam is shifted to a separate area where it is allowed to cool down. This condenses the vapors into liquid once again, retaining all minerals, and becoming ready for consumption. If distillation is integrated with carbon filters, 99.9% pure water can be extracted. Though these systems require an external heat source to carry out the process, they are certainly reliable as well as efficient.

4.Ultraviolet Light

The use of UV light as a purifier has gained prominence, typically for mobile apps like back packing. In this process, no removal of contaminants is done or no heat is applied from an outside source. Instead the harmful microorganisms are destructed completely. When used with another screening method, this method of purification works exceptionally well. And one can expect great use of this filtration process in the future. However, at present this process is avoided for filtration as it cannot remove chemicals or corrosive substances.

The bottom line is, there are different kinds of filtration systems used for removing different pollutants – however there isn’t a single method that can eliminate all pollutants from water. Because of this, one has to use a combination of two or more processes in household chores. So, when looking for water filters, be really careful. With regular maintenance, you must keep the water filter in great shape!