How to Descale an Espresso Machine

Scale is the chalky mineral deposit that builds up inside kettles and espresso machines. You can’t see most of it, but it affects temperature, pressure, and eventually whether the machine works at all. Descaling regularly is the cheapest way to keep a machine running for years.

Why Scale Builds Up

Tap water contains dissolved calcium and magnesium. When water is heated, those minerals come out of solution and stick to hot surfaces like boilers, heating elements, and narrow pipes.

Over time, scale insulates the heating element, so the machine has to work harder to reach temperature. It also narrows water paths, which can reduce flow and change shot timing.

How Often to Descale

It depends almost entirely on your water. As a rough guide:

• Hard tap water: every 1 to 2 months
• Moderate water: every 2 to 3 months
• Filtered or soft water: every 4 to 6 months

If you’re not sure how hard your water is, inexpensive test strips will tell you in seconds. Choosing better water for coffee in the first place can cut your descaling frequency dramatically.

Signs You’re Overdue

Watch for these:

• Shots running slower than usual with no grind change
• Steam pressure dropping during milk steaming
• The machine taking longer to heat up
• White flakes in the drip tray or water tank
• Coffee tasting flat or slightly bitter

Choosing a Descaler

Use a descaler made for espresso machines. Citric acid and lactic acid products are common and safe for most home machines.

Avoid vinegar. It works on scale, but the smell lingers in the machine, and it can be harsh on rubber seals. Check your machine’s manual too. Some manufacturers specify a particular product, and using something else may void the warranty.

Step-by-Step Descaling

This process works for most single-boiler and thermoblock machines. Dual boiler machines often have a different procedure, so check the manual first.

1. Empty and clean. Remove the water filter if your tank has one. Empty the drip tray.
2. Mix the solution. Follow the descaler’s instructions for dilution. Fill the tank.
3. Run it through. Turn the machine on. Run about half the tank through the group head and half through the steam wand, in short bursts.
4. Let it sit. Turn the machine off and wait 15 to 20 minutes so the solution can dissolve deposits.
5. Finish the tank. Run the rest of the solution through.
6. Rinse thoroughly. Fill the tank with clean water and run at least two full tanks through the group head and wand.

Taste a small amount of hot water from the group at the end. If it tastes sour or chemical, rinse again.

Descaling vs. Backflushing

These are different jobs. Descaling removes mineral buildup from the water side of the machine. Backflushing removes coffee oils from the group head and valve.

You need both. Backflushing every week or so keeps flavors clean and helps prevent bitter espresso. Descaling every few months protects the boiler and heating element.

After Descaling

Your first shot might run slightly faster than before, since the water paths are clearer. You may need to adjust your grind size a notch to dial in espresso again.

Note the date somewhere you’ll see it. A sticker on the back of the machine works fine. That way you won’t have to guess when the next one is due.