Is it OK to reboil water... or do I need to refill and start fresh with cold water each time?
At a recent coffee class, Meghan asked about reboiling water and if it is OK to reheat a still warm kettle. Good question!
I wanted to say that we shouldn't reboil a kettle but wasn't sure why. After the class, I did more research. As it turns out, it is fine to reboil your kettle.
As long as you are using good quality, clean-tasting water in your kettle (and why wouldn't you?), it can be reheated and will not affect the taste or quality of your coffee. Or your tea. Despite what your granny or British relatives say.
However...
As with all your coffee equipment, you should keep your kettle clean inside and out. This means regularly dumping out the old water and replacing it with fresh.
If you keep adding water and reboiling without ever cleaning or rinsing it inside, you will get mineral buildup from the evaporated water (steam). In fact, you may get mineral deposits even if you are regularly rinsing it, depending on the mineral content of your water.
If you do get mineral buildup in your kettle, it can be cleaned using vinegar or lime / lemon juice. In most of Canada, we have great quality water and this doesn't need to be done as frequently as they recommend.