Cleaning kettle

My kettle has lime scale built up after using it for awhile. This is because the water is hard here. A problem, which I don't face back home.

So I've been researching on how to clean these nasty brown lines. Most people suggested vinegar. But I do not want the kettle to smell vinegar since this kettle belongs to the serviced apartment. So I decided to try lemons.

Following instructions, I cut a lemon into 4 slices. Fill up the kettle to max and squeeze all the lemon juices into the kettle and dump the 4 slices of lemon into the kettle. Brought it to boil.

After it boiled, I left it for an hour while I continue working on other things.

After that, I boiled the water again.

Wahlau! It's as clean as it can gets!