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Guide · Descaling and cleaning

How to descale a Sage Dual Boiler (BES920)

How to descale the Sage Dual Boiler BES920, from Sage's UK manual: cooling down, the descale menu, draining both boilers through the valves, and the two flushes.

By Hoppin Hopper editorial teamUpdated Prices checked 4 min read

A Sage Dual Boiler descale takes more work than on most home machines. There’s no single button. Instead, you put the machine into a descale mode, drain both boilers through two valves on the front, run a descaling solution through, and then flush it out twice. It’s not difficult, but it takes most of a day once you count the cooling time. We haven’t tested this in person. Everything below comes from Sage’s UK instruction manual for the Dual Boiler (BES920), read on 3 Oct 2026. Read how we compare.

Sage Dual Boiler descale: the short answer

  1. Switch off and let the machine cool for at least 4 hours.
  2. Enter descale mode from the button menu.
  3. Drain both boilers through the valves behind the front cover.
  4. Run Sage descaler through for 20 minutes, then drain.
  5. Flush with fresh water twice, draining each time.

Who it isn’t for: owners of the Oracle, Oracle Touch or Oracle Jet. Their steps differ, and we cover them in our guide to descaling a Sage Oracle.

What you need

  • Sage descaler. The manual asks for one sachet of Sage Descaler dissolved in 1 litre of warm water. Sage’s “the Machine Descaler” pack of six was £16.95 at Sage UK, checked 3 Oct 2026, and Sage lists the BES920 among compatible machines. See it at Sage UK
  • A flat-head screwdriver to open and close the valves.
  • A cloth to lay over the drip tray.
  • Time. At least 4 hours of cooling, then three 20-minute cycles.

How to descale a Sage Dual Boiler, step by step

These are the steps from the BES920 manual, in our own words:

  1. Cool it down. Empty and refit the drip tray, switch the machine off and let it cool for at least 4 hours.
  2. Open the descale mode. With the machine off, hold the 1 CUP button, then press POWER, and hold both for 3 seconds until “rSEt” shows. Use the UP and DOWN buttons to reach “dESC”, then press MENU to confirm.
  3. Uncover the valves. Remove the DESCALE ACCESS cover on the lower front of the machine and lay a cloth over the drip tray.
  4. Drain the boilers. Using a flat-head screwdriver, slowly open the right valve. Steam and hot water may come out. Close it once it has drained, without overtightening, then repeat with the left valve.
  5. Add the descaler. Empty the drip tray, which may be hot. Empty the water tank and take out the filter. Dissolve one sachet of Sage Descaler in 1 litre of warm water and pour it into the tank.
  6. Run the descale. Press 1 CUP. The machine runs a 20-minute descale, filling and heating both boilers with the solution.
  7. Drain again. Empty both boilers through the valves, as in step 4, and empty the drip tray.
  8. Flush twice. Rinse the tank, fill it with fresh water, press 1 CUP and let the 20-minute flush run. Drain the boilers again, and repeat the flush once more.
  9. Finish. Press POWER to leave descale mode, refit the cover and refit the filter.

Who it isn’t for: anyone in a hurry. If you need coffee today, start the cool-down the night before.

Descaling versus the cleaning cycle

The Dual Boiler has a separate cleaning cycle. The manual says a cleaning alert appears on the display after about 200 shots. That cycle uses the cleaning disc and a cleaning tablet in the group head to clear coffee oils. It doesn’t remove limescale, so it doesn’t replace descaling.

Who it isn’t for: if your problem is bitter or oily-tasting coffee rather than slow flow or scale, the cleaning cycle may be the job you actually need.

How to descale less often

  • Set the water hardness. The manual has you test your water with the strip in the box and set a hardness level from 1 to 5 at first use. The default is 3.
  • Change the filter on time. The manual says every 3 months or 40 litres. That figure is based on hardness level 4, and it can stretch to 60 litres in a level 2 area.
  • Keep the tank fresh. Empty and refill the tank rather than topping up old water.

Downsides to know about

  • It’s slow. Four hours of cooling plus about an hour of cycles.
  • Hot water. The valves can release steam or hot water, so open them slowly.
  • No vinegar in the manual. Sage’s instructions call for its own descaler, so we haven’t suggested alternatives.
  • The older four-sachet pack is discontinued. Sage UK marks its “Descaler pack of 4” as discontinued, so look for the six-pack instead.

Where to go next

FAQ

How often should you descale a Sage Dual Boiler? When the machine or your water calls for it. Setting the right hardness and changing the filter on time reduces how often you need to.

Why does the Dual Boiler need its valves opened? It has two boilers, and the manual’s method drains each one through its own valve so the descaling solution can fill them.

Do you need to remove the filter? Yes. The manual has you take it out before adding the descaler.

Is the cleaning alert the same as descaling? No. It’s a separate cleaning cycle for coffee oils.

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Topics

  • Espresso at home
  • Coffee machines

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