My DeLonghi automatic coffee machine insists on being descaled at regular intervals, despite the fact that I use rain water and no scale can form. It does so by illuminating an indicator light hidden below the grind adjustment knob:

In addition, the instructions are so appallingly bad that it takes me 15 minutes to fight my way through them even before I can start. Here's what needs to be done:

1. Turn machine off, remove grounds.
2. Fill water container with 100 ml descaler and fill to the top with water. I use just water.
3. Place a 1.8 litre container (not supplied) under the output spout and cappucino spout. Turn on. Turn on the steam tap at top left (270°, marked 1).
4. After about 25 minutes, the liquid will have been processed. Turn tap to mark 0 (0°), drain container, rinse the water container and fill again. Replace, turn tap to 1.
5. After a few minutes, the flush is complete. Repeat exactly: Turn tap to mark 0 (0°), drain container, rinse the water container and fill again. Replace, turn tap to 1.
6. After a few minutes, the flush is complete, and the red LED goes out. Turn tap to 0. Done!