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Descale a coffee maker every 2 to 3 months on typical tap water. Tighten that to monthly if your water is hard, and stretch it to every 4 to 6 months if you brew with soft, filtered, or bottled low-mineral water. The interval is driven almost entirely by one variable, the mineral content of your water, plus how much you brew; the machine type mostly changes how fast the symptoms show up. If your machine has a descale light or counter, trust it after you set the water hardness level it asks for during setup.
Cadence by water hardness
The USGS classifies water at 0 to 60 mg/L of calcium carbonate as soft, 61 to 120 mg/L as moderately hard, 121 to 180 mg/L as hard, and above 180 mg/L as very hard (USGS water hardness). Your utility's annual water quality report lists your number, or a cheap test strip gets you close enough.
| Your water | Hardness (as CaCO3) | Descale interval (daily brewing) |
|---|---|---|
| Soft or well filtered | 0 to 60 mg/L | Every 4 to 6 months |
| Moderately hard | 61 to 120 mg/L | Every 2 to 3 months |
| Hard | 121 to 180 mg/L | Every 1 to 2 months |
| Very hard | More than 180 mg/L | Monthly |
Brew twice a day instead of once, or keep a machine that holds water hot all day (a BUNN, for example), and you move up one row. Want the math done for your exact setup? The free descale schedule generator turns your hardness and brew volume into a dated schedule.
The symptoms that outrank any calendar
Scale announces itself the same way on every machine: brew cycles slow down, the pump or boiler gets louder, pots come out short or lukewarm, espresso machines lose steam pressure, and eventually white flakes appear in the cup. Any of those means descale now regardless of when you last did it. The mechanism is simple: calcium carbonate insulates the heating element and narrows the water path, so the machine runs cooler and works harder at the same time.
Waiting for the light is usually waiting too long
Machines without sensors (most drip machines, moka pots, basic single-serve brewers) give you no warning at all, which is why the calendar matters most on the cheapest machines. Machines with descale lights typically count water volume against the hardness setting you gave them at setup; leave that setting on its default and the light can be badly wrong in either direction. And a water filter in the tank, charcoal or brand cartridge, slows scale but never stops it; filter changes and descaling are two separate jobs. When you do descale, use a citric acid solution rather than vinegar (citric descaling solution): the citrate salts rinse out cleanly while vinegar lingers and is harsher on seals. Better source water stretches every interval on the table; see the water guide.
Related reading
FAQ
How often should I descale my coffee maker? Every 2 to 3 months on typical tap water with daily brewing. Go monthly on hard or very hard water, and every 4 to 6 months on soft or filtered water.
How do I know if my coffee maker needs descaling? Slower brew cycles, a louder pump, short or lukewarm pots, weak steam on espresso machines, or white flakes in the cup. Any of these means descale now.
Does using filtered water mean I never have to descale? No. Filters reduce mineral load and stretch the interval, but they do not remove it entirely. You still descale, just less often.
Hardness classifications per the USGS Water Science School page linked above.
Never miss a cycle: the free one-page Machine Maintenance Calendar (PDF) puts every daily, monthly, quarterly, and yearly task for espresso machines, drip, Keurig, and moka pots on a card you can tape inside a cabinet.
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