Most bean-to-cup and many espresso machines take a cartridge filter in the tank.
What they do
Reduce hardness by ion exchange, so less calcium is available to form scale.
Remove chlorine and improve taste.
Some also add small amounts of magnesium.
Do they work
Reasonably, within limits. They are sized for a couple of months of household use and their capacity is finite.
A filter left in past its life does nothing, and can be worse than nothing as it becomes a biofilm site.
The costs
Proprietary and expensive. Manufacturers price them accordingly, and over a machine’s life the cartridges can cost as much as the machine.
The alternatives
A jug filter and fill the tank from it. Cheaper cartridges, and it works for tea and cooking too.
Bottled water with suitable mineral content — low bicarbonate, moderate hardness.
Recipe water — distilled or RO water plus a measured mineral sachet. Precise, and the best-tasting option.
The one thing not to do
Distilled or RO water alone. It makes flat, hollow coffee, and in some machines it interferes with water-level sensors that rely on conductivity.
If you use the built-in filter
Set the machine’s hardness setting to match, so the descale counter is calibrated correctly.
Replace it on schedule, and remove it before descaling — descaler destroys it.
The point
However you do it, do it. Scale is what kills machines.
Last reviewed 8 August 2026