Descaling of tea and coffee machines: put some vinegar in it, dilute with water and boil it! Flush it with water a few times afterwards otherwise the tea will taste like vinegar
I do the descaling of my coffee or tea pot with citric acid. I use powdered citric acid for the job. It doesn't smell and works better than when using vinegar. Also it's better for the rubber parts. I descale the washer once a month at 90 degrees Celsius with citric acid.