Limescale and hard water
Furred kettles, cloudy tea, white spots on glassware. The most common reason anyone buys a filter jug outside North America.
Filter jugs handle this wellHard water is water carrying dissolved calcium and magnesium picked up from chalk and limestone. It is not a health problem — plenty of the world drinks it happily — but it wrecks kettles, leaves a scum on tea, and puts a film on glassware that no amount of washing removes. Ion exchange resin in a filter cartridge swaps those hardness ions out, which is why the same jug that does nothing for fluoride is transformative for a kettle.
How you know you have it
- White crust inside the kettle within weeks of descaling
- An oily-looking film on the surface of black tea
- Cloudy spots on glasses straight out of the dishwasher
- Soap and shampoo that will not lather
What works
Any cartridge with an ion exchange stage, which is nearly all of them. Where they differ is how much of the capacity is given over to hardness rather than taste — Brita's Limescale Expert and Extra Lime Protection grades bias towards it, and Aquaphor's high-capacity cartridges hold up well in genuinely hard areas.
What does not
Filter-as-you-pour cartridges. There is not enough contact time with the resin to make a real difference to hardness.
Cartridges that reduce limescale
Ordered by strength of evidence, not by brand. An independently certified claim outranks a lab-tested one, which outranks a manufacturer’s word for it.
Cartridges that do not
These make no claim here, and that is not a criticism — it is what their manufacturers say. Buying one of these for this problem is the mistake.
Questions
Does a filter jug remove limescale?
Yes — this is one of the things a filter jug does well. Any cartridge with an ion exchange stage, which is nearly all of them. Where they differ is how much of the capacity is given over to hardness rather than taste — Brita's Limescale Expert and Extra Lime Protection grades bias towards it, and Aquaphor's high-capacity cartridges hold up well in genuinely hard areas.
What does not work: Filter-as-you-pour cartridges. There is not enough contact time with the resin to make a real difference to hardness.
Is limescale a problem where I live?
Hardness is entirely local. South-east England, much of Germany, Spain and the American Midwest are hard; Scotland, Ireland, Scandinavia and the American Pacific Northwest are soft. Your water supplier publishes the figure for your postcode or ZIP code, and it is worth looking up before you buy anything.