How the Different Types of Water Filters Work

Different types of water filters each have their own way of solving the problem of water pollution. Today, we’ll take a quick look at how they each go about doing their job.

How Different types of Water Filters Work

Activated Carbon


Many types of water filters employ a stage of activated carbon filtration at some point in the process. There are whole house water filters, reverse osmosis filters, pitchers, and faucet mounted filters available that have a stage of carbon filtration.

The activated carbon comes in the form of a charcoal like substance. The charcoal is very porous and acts as a sponge that absorbs impurities from the water. As the pieces of charcoal are very small with many nooks and crannies, they have a huge surface area which is very effective at absorbing the pollutants. It is an effective way of reducing chlorine-based impurities, but is ineffective against heavy metals, and water that produces lots of limescale. These filters have to be replaced when the charcoal is no longer effective.

Check out our water filter pitcher and faucet filter guides to read more about these type of filter.

Reverse Osmosis


Reverse osmosis involves forcing contaminated water through a very fine membrane. The pure water is allowed to pass, while the larger contaminant particles are removed by the filter.

Reverse osmosis is probably the most wasteful of the water filter processes (it uses water to produce clean water), but also one of the most effective. By incorporating a pump, and alkaline pH filter into a system, the main drawbacks of RO can be minimized.

Check out our reverse osmosis reviews.

Water Ionizers


Water Ionizers are great at making the water “softer”, and removing the limescale. They work by splitting the atoms of water contaminants to make ions (ions are electrically charged atoms with too few or too many electrons). These ions are then caught by the filter, and replaced with “nice” ions. To make these chemical process work, most water ionizers need to be filled with a special kind of salt.



Distillation involves the boiling of water, and then the collection of the water vapor. It is based on the fact that pure water will boil at a lower temperature than a lot of the contaminants. This means the water vapor will escape, leaving behind a lot of the contaminants. The water vapor can be cooled down again to form water. A downside to this process is that not all of the contaminants boil at a higher temperature than water. This means that they may be collected as “pure” water too.

We specialize in whole house water filters and reverse osmosis water filters here at If you would like to see which RO systems are worth looking at, then please check out our website awards. We also have whole house water filter reviews and awards.

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Hi I'm Jamie, teacher and owner/chief contributor at We strive to bring you the most informative water filter reviews in the most intuitive and user friendly way. Besides offering advice on the water filter to suit your needs, we also post topical articles on water pollution and the environment. Stay connected and follow us on, Facebook, Twitter, Google+ and more!

  1. Reply
    Sico, Flaviano Javier August 10, 2019 at 10:47 am

    how about those table top filters where the first stage is a half a ceramic sphere, then goes through a column of activated charcoal, two layers of sand and beads. There is also a layer of limestone rocks that they say gives the product water its better taste due to the added dissolved solids.

  2. I used to work as a Maintenance Engineer with Aramco back in the 80s. We have large camps for the construction crew and the support personnel. Our system is an RO plant that provided drinking water and raw water for general use in the camps that houses several thousand people.

    To adjust ph, we use regular sulphuric acid, and to adjust it, we add raw water. Is that alright?

    Just wondering.

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