Place a 1 liter or larger container under the cappuccino frother.
Empty the water tank and then refill it with 1 qt. of water. Add a bottle of Delonghi Descaler to the tank.
Press the "On/Off" power button. Wait for the "1-cup" and "2-cups" lights to glow green.
Push and hold the "Rinse and Decalcification" button under the "Decalcification Warning" light for at least five seconds. If your machine is working correctly, the light stops flashing and glows steadily and the "1-cup" and "2-cups" lights turn off.
Grasp the "Steam" knob and turn it left halfway for the cycle to begin. The solution runs through the tube and out the frother in spurts as the cycle runs.
Return the "Steam" knob to its original position when the "Water Empty/Missing" light turns on.
Dispose of the solution when the cycle ends. Rinse the container thoroughly. Return it to its spot under the frother.
Remove the water tank. Rinse it thoroughly with hot water. Refill it with fresh water and return it to the machine.
Turn the "Steam" knob left halfway. Wait for the machine to heat the water and cycle it through the tube into the container. The "Decalcification Warning" light will turn off. Return the "Steam" knob to its original position.
Discard the water in the container. Refill the water tank. Brew your beverages as desired.