Use the descaling kit or some white vinegar:
• Use some descaling solution diluted in half a litre of water or use 25cl of white vinegar in half a litre of water.
• Pour the solution into the water tank (without coffee),
• Start the cycle (without any coffee). After 2 minutes, stop the cycle manually. Leave the coffee maker for an hour,
• Restart the coffee maker to finish the cycle,
• To rinse the machine, run 2 cycles with water but without coffee.
Repeat the complete descaling operation, if necessary.