Under-sink drinking water filters
A filter housing plumbed into the cold supply under your kitchen sink, feeding either your existing tap or a separate filter tap. The most popular way to get filtered drinking water in a UK home.
An under-sink filter sits in the cupboard, out of sight, and treats only the water you drink and cook with. That focus is the point: you are not paying to filter the water that flushes the toilet, and a cartridge treating maybe fifteen litres a day lasts far longer than one treating the whole house.
Most systems are one or two cartridges in a housing, fed from the cold tap's isolation valve. The filtered water comes out either through a small dedicated tap drilled into the worktop, or — on a three-way tap — through the same spout as everything else.
For the majority of British households worried about taste, chlorine or the smell of their tap water, this is the right answer. It is not a limescale solution: an under-sink carbon filter does very little to hardness, and if scale is your problem you want the scale management pages instead.
Best for
- Improving the taste and smell of drinking water
- Removing chlorine
- Households getting through a lot of bottled water
- Renters, if a three-way tap is avoided and the system is removable
- Anyone who wants filtered water without a jug on the worktop
Common in offices and small cafés, though anywhere serving the public will usually want a higher-flow system and a documented maintenance record.
Pros and cons
Pros
- Out of sight, no worktop clutter
- Much cheaper per litre than a filter jug and far cheaper than bottled
- Cartridge changes are typically twice a year, not monthly
- Wide choice at every price point
Cons
- Needs a plumbing connection and space in the cupboard
- A separate filter tap means drilling the worktop, which is not reversible
- Does almost nothing for limescale
- Cheap systems use proprietary cartridges that get expensive
Can you install it yourself?
Yes, this is a realistic DIY job
Skill level: Moderate · Time: about 1.5 hours
The plumbing itself is straightforward push-fit work off an existing isolation valve. What catches people out is the tap hole, not the filter.
Tools you will need
- Adjustable spanner
- Pipe cutter or hacksaw
- PTFE tape
- Bucket and towels
- Drill with a suitable hole cutter if fitting a separate tap
Call a plumber if
- You need a new tap hole drilled in a granite, quartz or composite worktop — chipping is expensive and permanent
- There is no isolation valve on the cold feed
- The pipework under the sink is old copper or lead
Maintenance
Change cartridges every six months, or sooner if flow drops noticeably or taste returns. Sanitise the housing at each change.
Replacement interval: roughly every 6 months, though volume matters more than time. More on cartridge intervals.
What installation costs
£120–£250 indicative UK labour
Labour only, assuming an existing tap hole and accessible isolation valve. Drilling a new hole in stone worktop adds to it.
