The failure is gradual, which is why it is missed.
What actually happens
Calcium precipitates on the heating element as the water boils. The layer insulates, output falls, the machine takes longer to reach pressure and delivers wetter steam. Owners describe it as “not as good as it was” — which is exactly right, and entirely preventable.
Set the interval by hardness, not by habit
Look up your hardness band, take the manual’s interval for it, and put it in a calendar. A machine used weekly in a hard-water area needs attention several times a year.
If your machine takes a cartridge
Use it, and price replacements before choosing the brand — on cheap machines the annual cartridge cost can outrun the sense of the machine. An exhausted cartridge fails silently: the water simply stops being treated.
Distilled water is the other answer
Effective, and a nuisance to keep buying. On a small handheld with a 200 ml tank it is entirely practical; on a two-liter boiler it is not.
What not to use
Household vinegar, whatever the internet says. Manufacturers advise against it because it attacks seals and light alloys at concentrations that do little to hard scale.
The questions we hear
How do I find my water hardness?
Most water suppliers publish it by postcode. That number decides your interval: in a soft area an occasional descale is enough, in a hard one the manual's shortest interval is the right one and it is not optional.
Cartridge or powder?
A cartridge treats the water before it is heated, so scale never forms; powder dissolves scale that has already formed. Prevention is better for the machine and costs more over time — and no descaler reaches an element that is fully blocked.
Last reviewed 2026-08-15