A. If you notice that your single-serve or dual coffee maker isn’t working as well as before, the machine may need a thorough cleaning. For this purpose, you can descale the brewer using a water and vinegar solution. If this doesn’t fix the problem, you should check the drain hole to see if there is a blockage. Multiple uses of the coffee maker can often lead to the drain hole getting blocked, which can cause the brewer to work inefficiently.