|this is a limestone from water kettle : images from google|
I usually got problems with Sara's coffee maker. Though I cleaned it but something clogged inside that made the coffee tasteless and runs very slow. I rang the company for this matter because I thought its a machine problem. The company sent their man to fix the problem and explained me the reason why its clogged up.
Dried coffee oils can ruin the taste of even the best blend. In addition, "hard water", minerals can build up inside your coffee maker. So he said, as an alternative to coffee cleaners is to run a solution of half white vinegar and half water through the coffee maker to dissolve scale. The heated solution may have to be run through the unit one or more times if build up is heavy. Thoroughly rinse all parts of the unit. Run plain cold water through a cycle to remove all traces. If you still have your owner's manual, check it as well for instructions specific to your model. The glass pot, filter container and other removable components can be cleaned when you're washing the dishes. Do it a at least once a month to avoid the hard minerals that develop inside the machine.
It's the same with your water kettle, you can pour 1 inch of vinegar into it and then add 2 inches of water then bring to boil for 10 minutes. Be careful because its foam up but it will clean your kettle like new. Try it I can guarantee the result.
Another important point to note (as to speak) that cleaning your kettle is good for energy bill. The total amount of energy it uses is large and a clogged, limescale full kettle will require a lot more energy to boil. Therefore only fill the kettle with as much water as you require each time you boil and keep it clear for great drinks and refreshing aid to your electricity bill.