Descaling coffee makers, kettles and espresso machines

Hard water leaves minerals behind every time it's heated. Inside a coffee maker those minerals build up as limescale in the heating element and the narrow tubes that carry water. Over time the machine heats less efficiently, pumps more slowly, and starts making smaller or cooler cups.

Descaling dissolves that buildup. It's the most effective maintenance you can do on any machine that heats water.

Signs it's time

• Cups come out smaller than the size you selected
• Brewing takes noticeably longer
• The coffee isn't as hot as it used to be
• The machine makes more noise than usual
• You can see white or chalky deposits in the reservoir or kettle
• The descale indicator is lit

How often

Manufacturers typically suggest every one to three months for espresso machines and every three to six months for drip and pod brewers. The real answer depends on your water. If your kettle gets crusty quickly, you have hard water and should descale at the more frequent end. Using filtered water slows scale down but doesn't stop it.

Descaler, vinegar or citric acid?

Commercial descalers are usually based on citric or lactic acid and are made to be safe for the seals and metals inside machines. White vinegar works on many basic drip machines, but it smells, takes a lot of rinsing, and some manufacturers say it can damage rubber seals or aluminum parts.

For espresso machines in particular, use exactly what the manual specifies. Several brands state that using other products can void the warranty, and espresso machines have more parts that can be harmed.

The general process

Every machine has its own sequence, and some espresso machines have a guided descale program. The overall pattern is similar though:

1. Empty the reservoir and remove any water filter.
2. Add descaling solution and water in the ratio on the bottle or in the manual.
3. Run the solution through the machine in batches, discarding what comes out.
4. Let it sit if the manual says so. This gives the acid time to work.
5. Rinse the reservoir and run several full tanks of clean water through.

Kettles

For electric kettles, fill to about halfway with water and a descaler or a spoonful of citric acid, bring it to the boil, let it stand, then empty and rinse two or three times. Don't scrub the heating plate with anything abrasive.

Common mistakes

• Skipping the rinse. Most complaints about sour coffee after descaling come from too little rinsing.
• Forgetting the filter. Descaler ruins charcoal water filters. Take them out first.
• Using too much solution. Stronger is not better, and it can harm seals.
• Waiting too long. Very heavy scale can block tubes completely, and then descaling may not clear it.