How we test
Every product in our comparisons is assessed against the same list of criteria. This is how we work.
What we look at
Filter media and specification. We check what the filter is made of (for example activated carbon, ion exchange resin or a reverse osmosis membrane), its flow rate and how many litres a cartridge is rated for. A long list of claims on the box means little without a specification behind it.
Proof that it works. We look for independent certification against recognised standards, such as NSF/ANSI 42 and 53, and for the exact substances a product is certified to reduce. Where there is no certification, we say so.
Ease of use. We consider how easy the product is to fit, fill, clean and refill, how much space it takes up and how clearly the cartridge change is signalled.
User reviews. We analyse the experiences of people who use the product at home, paying particular attention to recurring problems such as leaks, slow filtering or cartridges that are hard to find.
Safety and quality. We check the materials in contact with water (for example BPA-free plastics), information about the manufacturer and the instructions for safe use and maintenance.
Cost per litre. We compare the running cost — replacement cartridges spread over the litres they filter — not just the price of the starter kit.
How to read our rankings
The order in a ranking reflects the overall assessment against the criteria above. For every product we describe its strengths and weaknesses, so you can match your choice to your home: the hardness of your water, how much you drink and how much space you have in the kitchen.
No filter fixes every problem. If you suspect a specific issue, such as lead pipes, start by contacting your water company, which can test the water at your kitchen tap.
We update our rankings when new products appear or when we learn something new about the ones we have already described.