Instructions: Given the background description of some cooking related query, summarize the question into a title
Input: I usually throw away the remaining water in the electric kettle before refilling it if the water is more than about a day old. In theory wouldn't boiling kill any impurities the old water might have? How long would the water stay drinkable in the kettle (assuming you boil it again before drinking)?
Output:
Is it safe to reheat old water in an electric kettle?