How to descale a coffee maker and an electric kettle

Hard water leaves limescale behind wherever it is heated. Inside a kettle it forms a white crust on the element and the base, and inside a coffee maker it builds up in the heating tube, the spray head and the pipes. Limescale slows the heating, uses more electricity, and gives the coffee a flat or bitter taste. It also hides bacteria and mold in the parts you cannot see. Descaling removes the deposit with a mild acid, and it is one of the simplest jobs in the kitchen once you know the steps.

Two acids do the job well for most people: white vinegar and citric acid. Both are safe for most machines when used as the maker allows. Always check the manual first, because a few models, particularly espresso and pod machines, have their own descaling product and their own instructions.

What you need

• White vinegar, or citric acid powder sold for descaling or for cooking
• Fresh water for rinsing
• A soft brush or a sponge
• A microfiber cloth
• A timer, so you do not forget the soak

For a kettle, you need enough liquid to cover the element. For a drip coffee maker, you need enough to fill the water reservoir at least half way.

Descaling an electric kettle

The kettle is the simplest of the two, and it takes about an hour from start to finish.

1. Empty the kettle and unplug it. Fill it with equal parts white vinegar and water up to the maximum line. If you use citric acid, follow the strength on the packet, which is usually about one tablespoon of powder to a liter of water.
2. Switch the kettle on and bring the liquid to the boil. Let it switch off by itself.
3. Leave the solution in the kettle for thirty minutes. For heavy limescale, leave it for an hour, but no longer, because prolonged soaking can damage some finishes.
4. Empty the kettle. Scrub the element and the inside base gently with a soft brush or a sponge to lift the loosened deposit. Do not use steel wool on an element, which can scratch its surface.
5. Fill the kettle with fresh water to the maximum line, boil it and empty it. Repeat this rinse once more. Two rinses are usually enough to remove the vinegar smell and taste.
6. Wipe the outside and the lid with a damp cloth, and dry the kettle completely before you put it away.

If your kettle is aluminum, check the manual before using vinegar, because acid can dull or mark some aluminum finishes. Citric acid is often a gentler option for those kettles.

Descaling a drip coffee maker

Many drip coffee makers have a descale or clean setting, and they tell you when to use it. If yours does, follow the on-screen steps and use the descaler the maker sells or recommends. If not, use the method below.

1. Empty the carafe and the filter basket. Remove the paper filter, the reusable filter and any pod holder.
2. Fill the water reservoir with a solution of equal parts white vinegar and water, or with the citric acid solution at the strength on its packet, up to the maximum line.
3. Start a brew cycle, but stop it halfway through. Most machines have a pause function, or you can switch the machine off at the wall and back on after thirty minutes.
4. Let the solution sit in the machine for thirty minutes. The acid works while it is still.
5. Complete the cycle, so the solution runs through the machine and into the carafe. Empty the carafe.
6. Fill the reservoir with fresh water and run a full brew cycle with no coffee in the basket. Empty the carafe. Repeat this at least twice more, until the water smells and tastes of nothing at all.

While the machine is descaling, wash the carafe, the filter basket and the lid in warm soapy water. Clean the spray head, which is the perforated plate above the filter basket. Pull it off if the machine allows, and clear the holes with a toothpick or a small brush. Blocked holes make uneven brewing, and a spray head that is full of limescale can cause the water to come out in a dribble.

Descaling an espresso or pod machine

Espresso machines and pod systems need more care, because they have steam wands, milk frothers and internal pumps that can be damaged by the wrong product. Use the descaling solution named in the manual, and follow its instructions exactly. Do not use plain vinegar in a machine where the manual does not allow it. If you are unsure, contact the maker before you start.

How often to descale

The right interval depends on how hard your water is. As a rough guide, descale a kettle every one to three months and a drip coffee maker every one to three months, and more often if the water is very hard. If you cannot tell how hard your water is, your local water utility can tell you, and many of them publish the hardness figure online.

Check the machine regularly. White crust on the element, a kettle that takes longer to boil, or coffee that tastes flat are all signs that descaling is overdue.

Getting the taste out

The most common complaint after descaling is a sour or vinegar taste. The fix is simple: rinse more. Run at least three full cycles of fresh water through a coffee maker, and rinse the carafe, the basket and the lid as well. For a kettle, two boils with fresh water are usually enough.

Before you brew your first cup of coffee, taste a little of the hot water from the machine. If it still tastes of vinegar, run another cycle of clean water. Citric acid leaves less taste behind, which is why some people choose it, although it works more slowly on heavy build-up.

Choosing between vinegar and citric acid

Both work by dissolving calcium carbonate, which is the main ingredient of limescale. Vinegar is cheap and easy to find, and it works well on most kettles and coffee makers. Its drawbacks are the smell and the taste it leaves behind, and it can be harsh on some rubber seals if it is used too strong or left too long. Citric acid is a powder that you dissolve in water. It has almost no smell, it leaves less taste, and it is gentler on seals, although it dissolves limescale a little more slowly.

For a kettle with heavy limescale, either works, and vinegar is fine if you rinse it well. For a coffee maker used every day, citric acid is often the easier choice, because it leaves less residue and makes the rinse quicker. Whichever you use, measure it, dilute it as described above, and follow the maker’s guidance on how often to descale.

Common mistakes

• Using undiluted vinegar. It is harsh on seals and it leaves a strong smell, so dilute it one part to one part with water.
• Leaving the solution in the machine overnight. Thirty minutes is enough for most build-up, and longer soaks can damage rubber parts.
• Forgetting the spray head and the carafe lid. Limescale collects in both, and they are the parts most likely to slow the flow.
• Skipping the rinse. A poor rinse is the cause of most bad-tasting coffee after descaling.
• Using a descaler not approved for your machine. Some products can damage seals and heating elements.

When to call a technician

If a kettle or coffee maker stops heating after descaling, if the water leaks from the base, or if you smell burning, switch it off, unplug it, and have it checked. Descaling should not damage a working machine. If it does, the cause is often a part that was already worn, and a repairer can tell you whether it is worth fixing.