Choosing a Water Filter for Your Kitchen

Begin with your water, not the box

Before you compare cartridges and cartridges' price tags, spend a week noticing what your tap water actually does. Does it leave a chalky ring in the kettle? Does a cup of tea taste slightly flat or metallic until you add lemon? Do you find yourself buying bottled water for the guests but drinking tap water yourself? Those small observations point quite reliably towards the right filter.

Hard water, common across much of southern and eastern England, carries dissolved calcium and magnesium. That is what furs up kettles, shower heads and coffee machine elements. Chlorine and chloramine, used to keep water safe on its journey to your kitchen, are the usual culprits behind that faint swimming-pool note. Older pipework can add a trace of metal taste. No single filter fixes everything perfectly, so decide which of these bothers you most — taste, limescale, or both — and let that guide you.

Jug filters: the gentle introduction

A jug filter is the cheapest way to find out whether filtered water changes your daily habits. You fill the reservoir, water drips through a carbon and ion-exchange cartridge into the jug below, and you keep it in the fridge door. Expect to pay somewhere between £15 and £35 for the jug itself, with replacement cartridges typically £5 to £10 each.

Taste-wise, jugs are good at removing chlorine and improving the flavour of tea and coffee. Most also soften water somewhat, which helps with kettle scale. What they will not do is remove everything dissolved in your water, and they do nothing about the limescale that builds up in your boiler or washing machine.

• Maintenance: a cartridge swap roughly every four weeks, or sooner in a busy household. Miss it and the filter can start tasting worse than the tap.
• Practicality: you need fridge space, and you need to remember to refill it. A family of four will empty one in a morning.
• Best for: renters, small households, and anyone testing the water, so to speak, before spending more.

On-tap filters: filtered water on demand

A tap-mounted filter screws onto your existing kitchen tap or replaces the aerator, and you switch between filtered and unfiltered with a small lever or diverter. Prices sit around £20 to £60, with cartridges usually £12 to £25, lasting roughly three months or a few hundred litres depending on the model and how hard your water is.

The appeal is convenience: no jug to refill, no fridge space used, and filtered water straight into the pan. Flow rates are slower than an unfiltered tap, though, and a low-pressure gravity system is noticeably leisurely. Some units reduce flow so much that filling a pasta pan becomes a test of patience. Check the flow rate figure before buying if you cook a lot.

On-tap filters handle chlorine well and many include a scale-reducing stage. They are also easy to take with you if you move, provided the new tap is compatible. The trade-off is visual: some people dislike the bulk perched on the spout.

Under-sink filters: the quiet workhorse

An under-sink system sits in the cupboard below and feeds a dedicated filtered tap on the worktop, or sometimes a separate small spout alongside your main tap. Installation is the main hurdle — you will generally want a plumber unless you are confident with compression fittings — and costs run from around £60 for a basic housing to £250 or more for a multi-stage or reverse-osmosis unit.

Cartridges are the bigger commitment here, typically £25 to £60, but they last far longer: six to twelve months is common, sometimes with a capacity measured in thousands of litres. That means fewer interruptions and less waste plastic over a year than a jug.

• Taste: generally the best of the three, particularly for chlorine, sediment and odour. Reverse osmosis goes furthest, stripping almost everything, which some people love and others find a little flat.
• Limescale: ion-exchange and reverse-osmosis systems genuinely reduce scale, protecting kettles, coffee machines and hot-water taps.
• Watch out for: reverse osmosis wastes water — often several litres for every litre produced — and removes minerals you might otherwise value.

What it really costs to run

Purchase price is the least interesting number. Think in cost per litre over a year. A jug with twelve cartridges might cost £80 to £120 annually for perhaps 1,200 litres. An on-tap filter with four cartridges lands in a similar range. An under-sink system might cost £50 to £90 a year in cartridges for several thousand litres — cheaper per litre, but only if your household actually drinks that much.

Set that against bottled water, where a litre can easily cost 50p or more, and almost any filter pays for itself if you currently buy bottles. The exception is a very low-use household: a cartridge that expires on time rather than on volume can be poor value if you only drink two glasses a day.

Matching the filter to your household

Ask three questions. How many people will draw from it daily? How hard is your water? And how much space and hassle can you tolerate?

• One or two people, renting, unsure: start with a jug. Low risk, immediate improvement in taste.
• Busy family, lots of cooking, limited fridge space: an on-tap filter keeps up better than a jug ever will.
• Homeowners with hard water and scale problems: an under-sink system, ideally with a scale-reduction stage, protects appliances as well as your palate.

Whichever you choose, buy cartridges in multipacks where it saves money, note the change date on the calendar, and clean the housing itself every few months. A filter is only as good as the routine around it — and a well-chosen one quietly becomes part of the kitchen you barely think about.