Descaling an Espresso Machine: How Often and How To

You can do everything else in our espresso guide perfectly and still pull bad shots from a machine full of scale. Descaling is dull, but it protects both your coffee and your machine.

What scale is

Scale is the chalky mineral deposit left behind when hard water is heated. It is mostly calcium and magnesium. You have seen it inside a kettle. The same thing happens in your espresso machine’s boiler, heating element and narrow pipes, where you cannot see it.

How scale affects your coffee

Scale acts like insulation. It makes the heating element work harder and can make temperature less stable. It also narrows the pipes and can partly block the solenoid valve or the shower screen.

In the cup, that can show up as:

• Shots that slowly get more sour even though your settings have not changed.
• Shot times that drift because flow from the group head is weaker.
• Uneven extraction if the shower screen sprays to one side.

If you have been adjusting your espresso grind size over and over without fixing a drifting shot, scale may be the real cause.

How often to descale

It depends on your water. As a rough guide:

• Soft water: every three to six months.
• Moderate water: every two to three months.
• Hard water: every month or so.

A simple water hardness test strip will tell you where you stand. Using filtered or softened water stretches the interval a long way.

A basic descaling routine

Always check your machine’s manual first. Some machines, especially those with dual boilers, have specific instructions or should only be descaled by a technician.

1. Empty the water tank and mix in a descaler made for espresso machines. Citric acid based products are common.
2. Run the solution through the group head and steam wand in short bursts, letting it sit between bursts.
3. Leave it for 15 to 20 minutes so it can dissolve the deposits.
4. Rinse the tank thoroughly and run at least two full tanks of fresh water through every outlet.

Avoid plain vinegar. It can damage seals and is hard to rinse away fully.

Clean the group head too

While you are at it, scrub the group head gasket and shower screen. A clean screen spreads water evenly across the puck, which makes your espresso tamping work as it should.

After descaling

Your machine may brew slightly hotter or flow slightly faster once the scale is gone. Pull a couple of test shots and expect to adjust your grind a little.

Keep reading

• Espresso brew ratio: re-checking your numbers after maintenance
• Espresso shot timing: spotting slow drift before it gets bad