We need water to survive, it’s as simple as that. But not all water is as clean as you might hope. And that’s where water filters come in. Our bodies, despite being solid, are made up mostly from water. This water needs replenishing regularly, and with clean water.

Thankfully, water is actually quite good at getting rid of minor pollutants itself, but it can’t do it all. In some places, water filters are an absolute necessity. They turn undrinkable water into water that’s safe to consume. If you live somewhere with drinkable tap water, filters might not be quite as crucial, but they can still be helpful in making the water you consume just a bit more healthy and less dirty. If nothing less, they’re good for extra peace of mind.

In this article, we’re going to look at how the main different types of filters actually work. There are four different types of water filters, and each of these use slightly different processes and technology to clean the water before you drink. Some of these are more suited to home filtration systems, while others are built for large-scale water filtration. Let’s have a look at the four different types of filters and how they work…

How do water filters work?

While there are four different types of water filters (we’ll look at them a bit more closely in a minute), water filters generally use two different methods to remove dirt and impurities from water. These are physical filtration and chemical filtration. Physical filtration normally has some sort of device or technology in-place to strain the water and remove large impurities. It’s a lot like a sieve in that way. You might have seen a coffee filter or one in the kettle, well it’s a similar idea and method to that, only with smaller holes. These filters can either be made from gauze or textile.

When you pour the water through a physical filter, most of the bigger impurities are removed by the filter. But that’s not the only method a filter can use. Chemical filters use chemistry and various solutions to help remove impurities in water. Some types of filters actually use both of these techniques, so let’s have a look at the four main types of filters:

Reverse osmosis

If you can still remember your science classes at school, you’ll probably have a reasonable idea about the osmosis process. With reverse osmosis filtering, dirty water is forced through a membrane filter at high pressure so that the impurities are left behind as the water moves through quickly.

The osmosis filtration needs energy to force water against its natural impulses, and this normally comes in the form of a pump. A complicated scientific process helps the water molecules rearrange themselves in order to leave dirt behind and remain clean.

Activated carbon

This is the most popular type of water filtration in homes across the country, and is sometimes known as AC filtration. The system is based around charcoal which as a massive internal surface and can actually absorb a lot of water (like a sponge). These internal surfaces can trap impurities when water is passed through, which is called absorption.

While carbon is a great basis for a home filtration system, it does have some drawbacks. For example, it isn’t great with hard water and limescale, as well as sodium, fluorine and some other minerals. As well as this, the filters can fill up over time and will need to be replaced after a while.

Ion exchange

Ion filters are good at removing limescale by making your water “softer”. These filters split the atoms of dirty substances apart to make ions. These ions are then removed and replaced with ions that aren’t contamintated. THis ion filter process might sound complicated, but it’s actually quite simple.

Ion exchange filters work because they’re made from lots of beads that contain sodium ions. When hard water enters the filter, the magnesium and calcium ions are split apart because of a chemical reaction between the sodium ions. The “dirty” magnesium and sodium ions in the hard water are trapped and replaced by sodium ions.

One issue with ion exchange filters is that they’re just replacing magnesium and calcium with sodium. This may make the water taste nicer and sfoter (leading to less problems with limescale), but it really is just another contaminant. Ion exchanges also obviously don’t work very well with soft water, or water that’s contaminated with something other than calcium and magnesium. Ion exchange filters also need their sodium ions recharged from time to time, normally by adding a special type of salt. That’s the same reason you have to add salt to dishwashers, as they use a similar process and stop the gradual building up of limescale.


Another common type of filtration that you might have already heard of is distillation. It’s one of the most simple methods of filtration, but also one of the most popular. And it’s based on something that’s been used for hundreds, if not thousands of years: boiling. When you boil water, the heat kills off tons of dirty bacteria and pollutions. However, this type of filtration doesn’t remove chemicals that might already have been in the water. That’s why distillation takes the boiling process to the next level by capturing the steam from boiled water and then condensing it back into a separate container. Because water boils at a lower temperature than many contaminants, they’re left behind in the process. However, not all impurities are removed by this process because they boil at a lower temperature than water.

If you really want to make sure your water is pure, you might want to use a combination of these methods. As you can see, they work in different ways and not all of these filtration methods are good with different types of contaminants. Depending on where you live and what your water is like, you might be able to stick to one of these specific types of filtration. At least now you know how they all work.

About the Author James S

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