How often should I descale my coffee machine?

If your machine counts litres and prompts you, follow it. Counting water is the correct measure, and the manufacturer knows its own boiler.

If it does not prompt, use your water hardness:

• Hard water, above ~150 ppm — every month or two.
• Medium, 50 to 150 ppm — every three months.
• Soft, below ~50 ppm — every six months, and scale is not really your problem.

Your water utility publishes hardness by postcode. Looking it up takes two minutes and settles this properly.

Why it matters more than it seems

Limescale does not announce itself. It deposits on the heating element and through the pipework, and the machine heats a little more slowly, flow drops slightly, temperature stability decays, shots get gradually worse — and you adjust without noticing. Then one day it stops.

A machine on hard water that is never protected typically reaches that point between year three and year five. The same machine, filtered and descaled, often passes ten.

Filtering does not replace descaling

This is the mistake that kills filtered machines. A jug or in-tank filter reduces carbonate hardness substantially, not to zero, so scale still forms — just far more slowly. Descale on schedule; you simply reach it less often.

Use a proper descaler

Citric-acid descalers dissolve scale quickly and rinse clean. Vinegar works slowly, leaves a smell in the boiler that takes many flushes to clear, and its acidity can attack seals over repeated use. A tub of descaler costs about the price of two coffees out.

Do not forget the other half

Descaling handles minerals. It does nothing about coffee oils, which build up in the group and turn rancid — that is what backflushing with a cleaning tablet is for.