Mineral buildup from hard water is one of the most common causes of a slow, failing espresso machine. Descaling regularly is the single highest-impact maintenance task you can do, and it takes about 20 minutes.
Hard water leaves mineral scale inside boilers and internal tubing, which restricts water flow, causes temperature instability, and can eventually damage heating elements entirely.
Every 1–3 months for machines used with hard tap water; every 3–6 months if you use filtered or bottled water. Check your machine's indicator light if it has one.
Mix a descaling solution (citric acid-based or a manufacturer-branded product) per the package ratio. Run it through the water reservoir and brew system in short cycles, following pauses to let the solution sit inside the boiler. Finish with several full reservoirs of plain water to rinse completely.
Breville and De'Longhi models with digital displays often have a guided descaling mode built in — use it rather than manual cycles when available. Gaggia and Rancilio's simpler machines require manual cycling through the steam wand and brew head.
Slower brew times, inconsistent temperature, or unusual noises from the boiler are common signs.
It's possible but not recommended — vinegar's smell and residue are harder to fully rinse than a purpose-made citric acid descaler.
Related reading: How to Backflush an Espresso Machine