Clean a Bunn coffee maker once every three months if you have hard water. Hard water leaves calcium and magnesium deposits inside your machine that affect its performance. Hard water leaves calcium and magnesium deposits inside your machine that affect its performance..Chances are, you don’t clean your coffee maker nearly as often as you should. A study found that most people have no idea just quite how dirty their coffee maker is..From home coffee makers to commercial coffee grinders and much more, find commercial home beverage products and accessories at BUNN..Bunn coffee maker troubleshooting There is nothing more frustrating than unpredicted problems with your Bunn coffee maker when instead of a cup of coffee, you receive just steam or water. Quite often, coffee makers stop working if the one way valve gets clogged, but there are also dozens of other possible problems..