Clean Your Tea KettleTo remove mineral deposits, boil equal parts white vinegar and water inside kettle. Remove from heat. Let sit several hours; rinse. Hand wash the pot’s exterior with a gentle pot-scrubber sponge. Let tap water run for a few moments before adding it to the pot. (source)
To anyone who owns a moka cup/‘greca’, this works too. I own a tiny espresso one and even with the convenience of microwaving the water, I’d rather brew my coffee/tea with it.