United Kingdom Water Treatment Association

Filters/Membranes

What is a drinking water filter?

A drinking water filter is an appliance used to alter the composition of water to improve its acceptability for drinking and cooking purposes - mainly with respect to its aesthetic quality: taste, odour, appearance. They are most commonly supplied as:

  • Jug filters these are filled from the kitchen tap and usually stored in the fridge.
  • Plumbed-in filters these are connected directly to the water supply, usually under the kitchen sink. A separate dedicated drinking water tap is installed at the kitchen sink, so that filtered water is available on demand.

Pouring water into a glass

What does it do?

There are a range of different drinking water filter technologies used individually or in combination. The most common are:

  • Activated Carbon Filter - used to reduce common organic, taste and odour contaminants – The carbon has a very large, active surface area which attracts and absorbs organic substances from the water. They are also commonly used to remove tastes associated with chlorine. The carbon can be in powder, granular or block form.
  • Ion Exchange - used to reduce the minerals associated with lime-scale formation and other metal-ion contaminants such as lead. Usually in the form of tiny beads or granules which function by exchanging the mineral or contaminant ions with (mainly) hydrogen ions.
  • Sediment Filter - designed to remove particulate matter from water. They comprise a mesh or cloth through which the water passes, trapping the sediment. The smaller the holes in the filter, the smaller the particles that can be removed.
  • Reverse osmosis - removes most of the dissolved mineral content by passing the water, under pressure, through an extremely fine membrane.
  • Distillation - removes most of the mineral content of the water by evaporating (boiling) it and condensing the water vapour.
  • Disinfection - used to reduce bacteria or other micro-organisms, e.g. with ultraviolet light or a very fine sediment filter (usually ceramic or membrane).

Why fit one?

Mains tap water in the UK is supplied and regulated to a very high standard, but because of concerns about taste, odour, cloudiness and, occasionally, adverse press publicity, people look to improve the quality to make it more appealing to drink. The most common complaints about tap water relate to chlorine which is often used by the water supplier to disinfect the water. Residual chlorine may result in a “bleach” type taste and some of the by-products of this disinfection (e.g. TCP) can also leave unpleasant taste or odour.

In hard water areas, scale deposits in the kettle or coffee maker and on hot drinks such as tea are a common complaint.

The quality of the water at the tap depends to some extent on the plumbing within premises which is usually the responsibility of the consumer. Some older properties still contain lead pipework which may contaminate the water supply. An appropriately selected water filter can significantly reduce lead contamination.

The benefits of water filtration include:

  • Clearer, better tasting, odour-free drinking water
  • Clearer, better tasting beverages such as tea or coffee with a more flavoursome aroma
  • Reduction in heavy metal content derived from plumbing materials, including lead and copper
  • Reduced lime-scale build up in kettles, coffee makers, etc.
  • Reduction of the dependence on bottled water(cost, transport, and bottle disposal)
  • Choice of the level of treatment with increased confidence in water quality

Is filtered water better for me?

In simple terms, water is essential for health and maintaining a good hydration level is increasingly being recognised as important for mental and physical performance. Good hydration can help prevent headaches, constipation, kidney stones, heart disease and certain cancers. If filtering tap water makes you feel more positive about drinking it, which in turn leads you to consume more, then it is considered beneficial.

Which filter is right for me?

This depends entirely on the particular quality of water you want to achieve. To improve taste, an activated carbon filter should be considered. To prevent lime-scale build-up in a kettle, an ion exchange filter would be suitable.

What should I do?

Work with a reputable supplier! They will advise which unit is appropriate to your specific requirements – begin by consulting the list of UKWTA members.

Little girl reaching for a glass

As you might expect, for plumbed-in devices, there are regulatory requirements to be complied with: the connection to the water supply must be fitted with a non-return valve and the drain connection for a reverse osmosis unit must have an air-break. UKWTA members will be able to help you understand the requirements. Remember that water filters do need regular attention (for example, periodic cartridge change) for optimum performance. Consult the manufacturer's instructions.