Water filters do a range of jobs to ensure that the water you drink is free of sediment, tastes great and is free from potentially harmful bacteria.

There are several different types of water filters that each serve to remove a different impurity or affect the quality of water in some way, and a home water filtration system will often feature several of these filters working in sequence.

Mechanical Filters

The oldest, simplest and most established water filtration system, mechanical filters use a physical barrier to remove particles of dirt, sediment and other molecules out of the water.

Whilst they are the oldest part of water filtration, they still have a hugely important purpose and modern filters are exceptionally sophisticated in nature, able to remove particles smaller than the naked eye, protecting from potential biological pathogens.

Absorption Filters

Sometimes simply known as carbon filters, as the exceptionally common element is almost always used for these types of filters, absorption filters feed water through either granulated activated carbon or a block of carbon that is filled with holes and marks that trap chemical impurities.


These filters work by isolating a substance using a chemical filter and are typically used to reduce the effects of limescale in hard water areas.

Typically, polyphosphate at a food-grade level is used to inhibit scales and works to keep the calcium and magnesium that make scale within the water solution itself, although there are other methods such as block salt or ion exchange that can be used for water softening.

Ion Exchange

The process of ion exchange works similarly to sequestration in that it stops limescale from forming, but unlike the latter, an ion exchange system physically removes the magnesium and calcium ions.

This is commonly used for machines that need to be kept at a high temperature, such as hot water dispensers and coffee machines, and commonly takes the form of a series of resin beads that are regularly recharged to maintain their effectiveness.

Reverse Osmosis

An increasingly popular system in water dispensers, reverse osmosis works by forcing water through a semi-permeable membrane under pressure so that most of the contaminants are left on one side and the water itself passes through the other.

Combined with other filters it is a highly effective way to provide water with almost no contaminants, although it does have the constraint that wastewater is produced as a by-product.