Jug, tap or under-sink: which water filter suits your home?

Tap water in the UK is among the most closely regulated in the world, and for most homes it is perfectly safe to drink straight from the tap. So why do so many people buy a water filter? Usually for one of three reasons: they do not like the taste or smell of chlorine, they live in a hard water area and are tired of limescale in the kettle, or they live in an older house and want extra peace of mind. The right filter depends on which of these matters to you.

Start with the question, not the product

Before you compare models, decide what you want the filter to do. The US Centers for Disease Control and Prevention puts it simply: match the system to the specific problem, and check the label for the substances a product is actually shown to reduce, rather than assuming every filter removes the same things. A filter that is excellent at improving taste may do little for limescale, and vice versa.

• Better taste and less chlorine smell — almost any activated carbon filter will help.

• Less limescale in the kettle — look for filters with ion exchange resin, which most filter jugs contain.

• Specific concerns such as lead — look for independent certification for that substance (more on this below), and talk to your water company first.

Filter jugs

A filter jug is the cheapest and simplest way to start. You fill the top reservoir, the water passes through a cartridge and collects in the jug below. Most cartridges sold in the UK combine activated carbon, which reduces chlorine and improves taste, with ion exchange resin, which reduces the minerals that cause limescale.

Good for: renters, small households, anyone who mainly wants better-tasting water and fewer flakes in their tea.

Watch out for: the small capacity (you will refill it often), the need to keep it in the fridge in warm weather, and the ongoing cost of cartridges, which typically need replacing about once a month. We explain this in detail in our guide on how often to change a filter cartridge.

Tap-mounted filters

These clip onto the end of your kitchen tap and usually have a lever that switches between filtered and unfiltered water. They filter on demand, so there is no waiting and no jug taking up space in the fridge.

Good for: people who want filtered water without refilling a jug, and who have a standard tap the filter will fit.

Watch out for: compatibility — many do not fit pull-out, spray or unusually shaped taps — and a slower flow when filtering. Check the fittings included before you buy.

Under-sink filters

An under-sink system sits in the cupboard below the sink and connects to the cold water pipe, usually with its own small drinking water tap on the worktop. Cartridges are larger, so they last longer than jug cartridges, often several months.

Good for: homeowners and families who drink a lot of water and want a permanent, out-of-sight solution.

Watch out for: installation. The Drinking Water Inspectorate advises consulting your water company before buying a plumbed-in device and having it fitted by a qualified plumber. You can find an approved plumber through WaterSafe, the UK register of approved plumbers.

Reverse osmosis

Reverse osmosis (RO) systems push water through a very fine membrane. According to the CDC, reverse osmosis can remove germs and a range of chemicals, including lead and copper. RO systems are usually installed under the sink and often combine several filter stages.

Good for: people with a specific concern about contaminants, or those who want the most thorough filtration available at home.

Watch out for: price, installation, the space needed under the sink, and the fact that RO systems send some water to the drain as part of the process. They also remove most minerals, which some people find changes the taste.

Whole-house filters and water softeners

A whole-house filter treats all the water coming into your home, while a water softener specifically removes the calcium and magnesium that cause limescale. Softeners can protect boilers, showers and appliances in hard water areas, but they are a different product from a drinking water filter.

The Drinking Water Inspectorate recommends keeping an unsoftened supply to the kitchen tap for drinking and cooking, because softened water contains more sodium. It also advises that artificially softened water should not be used to make up baby formula. If you are considering a softener, read our guide to hard water and limescale first.

How to compare filters fairly

Once you know which type suits you, compare models on the same points:

• What it is certified to reduce. Independent certification against recognised standards (such as NSF/ANSI 42 for taste and odour, or 53 for health-related contaminants) is more meaningful than claims on the box.

• Cartridge life in litres or months, and how easy replacement cartridges are to buy.

• Running cost per litre — the price of cartridges divided by the litres they filter. A cheap jug with expensive cartridges can cost more over a year than a pricier system.

• Fit and space — tap shape, fridge door shelf height or cupboard space under the sink.

• Maintenance — how often it needs cleaning, and whether there is a reminder for cartridge changes.

For a closer look at what different filter media can and cannot do, see our guide What does a water filter actually remove?

The short version

If you mainly want better-tasting water, a filter jug or tap filter is usually enough. If you drink a lot of water and own your home, an under-sink filter is more convenient in the long run. If you have a specific concern, such as old lead pipes, speak to your water company first and then choose a filter certified for that exact substance.