Coffee is 98 percent water. Often overlooked, the quality of the water is as important as the quality of the coffee. A good rule of thumb is that if your water doesn't taste good from the tap, it won't taste any better in your coffee. That's why Cuisinart suggests adding a water filter to the coffeemaker. The Cuisinart DCC-RWF charcoal water filter removes chlorine, calcium, bad tastes and odors, for the purest cup of coffee every time.