How to descale a coffee maker

1. Check whether it's time

Count brews or watch for the signs. Moccamaster suggests descaling around every 100 brews, "or whenever you come to the end of a box of filters." Bonavita says at least once every 100 uses. The OXO Brew 8-Cup lights its Clean button as a reminder after 90 brew cycles. A brewer that takes longer than usual, or steams more than usual, is also due. Hard water means descaling more often.

2. Choose a descaler, not a cleaner

Buy a coffee-machine descaler. Bonavita recommends "a good quality biodegradable and phosphate-free" one, and points out that descaler and cleaner are different products that "serve different purposes." For scale, you want the descaler. Moccamaster recommends Urnex Dezcal or BioCaf descaling powders.

Skip the vinegar. Bonavita says it "may not effectively descale your brewer," can be difficult to rinse thoroughly, and may leave an odour that affects the coffee. Urnex makes the same point about taste and rinsing.

3. Dissolve the descaler in a separate container

Mix the descaler with water before it goes anywhere near the brewer. For a drip coffee maker, Urnex's instructions are one 28 g packet in 32 oz of lukewarm water. Moccamaster also specifies 32 ounces of warm water and says to stir until all the powder dissolves.

Don't use hot water in the brewer. Moccamaster's warning is direct: "Never put hot water in your brewer." If you warmed the water to dissolve the powder, let it cool first.

4. Pour it in and run a brew cycle

Pour the solution into the water reservoir, put the empty carafe in place and run a brew cycle as if you were making coffee. Moccamaster says you don't need a filter.

Some brewers have their own descale cycle. On the OXO Brew 8-Cup, the manual says to fill descaling solution and filtered water no higher than the MAX line, remove any filter or single-serve accessory, screw the carafe lid on, set the mode switch to Carafe, then press Power and the Clean button. If your brewer has a cycle like this, use it, and follow its manual.

5. Discard the solution

Pour away what collects in the carafe. Don't drink it, and don't reuse it for a second pass unless your descaler's instructions say to.

6. Rinse with clean water

Run fresh water through the brewer until no descaler is left. Moccamaster and Urnex both say three full cycles of clean water. OXO's manual calls for a 5–8 cup water-only brew cycle after its Clean cycle, then discarding that water.

7. Put the next one on the calendar

Set a reminder based on how much you brew. Urnex suggests using its packets every 3 months for best results, which roughly matches 100 brews for one pot a day. If your brewer ran slowly before you descaled and runs normally now, note how long it took to get there and descale a little sooner next time.

Why not just use vinegar?

Coffee-maker brands say it doesn't work as well. Moccamaster says vinegar isn't strong enough to break down mineral buildup. Bonavita adds that it is hard to rinse out and can leave an odour that affects flavour. Urnex says vinegar takes longer to work and leaves "an unpleasant odor and aftertaste." If your brewer's manual gives its own instructions, follow those first.

Does descaling change how the coffee tastes?

It can. Moccamaster lists coffee that "doesn't taste as good" as one of the signs a brewer is due. Grind matters as much as the machine, though. If your coffee from a clean brewer still tastes off, check your grinder and setting: how to choose a coffee maker for your grinder covers matching the two, and the drip method guide covers grind size and ratio. If you're grinding for drip, the grinder finder can suggest a grinder that suits it.