Proper water, straight from the tap.

Under-sink water filtration for British homes

UK mains water is treated to a high standard before it reaches your kitchen, so the reason most households fit a filter is not safety — it is taste, chlorine odour, and the limescale that hard water leaves behind on kettles, glassware and coffee machines. Roughly three in five British homes are supplied from chalk and limestone aquifers, which is why the problem is so familiar across London, the South East, East Anglia and much of the Midlands, and far less common in Scotland, Wales, Cornwall and the North West.

An under-sink system treats water at the point you actually drink it. Unlike a jug filter, it does not need refilling, it does not take up fridge space, and the media volume is many times larger, so contact time is longer and the cartridge lasts months rather than weeks. Unlike a whole-house softener it needs no salt, no drain connection and no notifiable plumbing work, which makes it a realistic option in a rented flat or a compact kitchen.

Choosing between carbon, scale reduction and reverse osmosis

Activated carbon is the right starting point where the complaint is chlorine taste and odour: it is inexpensive, has no waste water and fits almost anywhere. Scale-reduction filters add a stage that keeps hardness minerals in suspension so they do not bond to hot surfaces, which is the sensible choice for hard water regions. Reverse osmosis goes furthest, rejecting the large majority of dissolved solids including lead, nitrates and fluoride, at the cost of a larger cabinet footprint, a waste line and a higher price. Our comparison guide sets the three side by side so you can match the technology to your supply rather than buying the biggest system available.

Fitting, running costs and what to expect

Every system we sell is designed to connect to a standard 15mm UK cold feed with push-fit fittings, and most customers complete the installation in under an hour without a plumber. Running costs come down to cartridges: carbon and sediment stages typically every 6 to 12 months, reverse osmosis membranes every 2 to 3 years, all stocked here and matched by model. Prices include VAT at 20%, UK mainland delivery is free with no minimum spend, every filtration system carries a two-year warranty, and returns stay open for 30 days from delivery.

How to tell which filter your kitchen actually needs

Start with the symptom rather than the specification sheet. If the kettle furs up within a fortnight and the shower screen dries with white spots, hardness is the dominant issue and a scale-reduction stage will make the biggest day-to-day difference. If the water tastes of swimming pool first thing in the morning, that is residual chlorine from the mains and a carbon block resolves it almost entirely. If you are in an older property with lead pipework, or you simply want the broadest possible reduction in dissolved solids before making up baby formula, reverse osmosis is the honest answer even though it costs more and takes more cupboard space. Households with a combination of complaints usually end up with a multi-stage system: sediment first to protect the later stages, carbon for taste, then either a scale inhibitor or an RO membrane depending on how far they want to go.

Measure your cupboard before ordering. A three-stage cartridge housing typically needs around 40cm of height for cartridge changes and roughly 15cm of width beside the waste trap; reverse osmosis cabinets need similar height plus room for a pressure tank about the size of a football. If your under-sink space is already occupied by a waste bin or a washing machine outlet, a compact inline carbon unit mounted horizontally on the cupboard wall is usually the only realistic route, and it still handles chlorine and sediment well.

What filtration does not do

We would rather be straight about the limits. An under-sink filter does not soften water for the whole house, so your boiler, shower and washing machine still see the same hardness they always did — a filter protects the water you drink and cook with, not the plumbing behind the walls. Scale-reduction media conditions minerals so they are less likely to bond to hot surfaces; it does not remove calcium and magnesium, and any product claiming otherwise without an ion exchange or RO stage is overselling. Carbon does not remove nitrates or fluoride, and no filter turns unsafe water safe on its own: UK mains supply is already tested to drinking standards by your water company before it reaches the stopcock.

Buying from Clarisink

We are a small UK-focused specialist rather than a general marketplace, so the range is deliberately short: a handful of systems that cover the realistic cases, plus the cartridges that keep them running. Every product page lists the flow rate, cartridge life, connection size and physical dimensions in the same format, so you can compare like with like instead of decoding marketing language. Reviews are published exactly as customers write them, including the critical ones, and we never write or purchase them. If you are unsure which system suits your postcode, send us your water company name and we will tell you the typical hardness for that supply zone and which filter we would fit ourselves.