Just like any coffee maker, regular descaling is crucial to not only keep the machine running smoothly longer, but for brewing great tasting coffee too. The DCC-T20 is pretty simple.  Fill the water reservoir with a solution of one-third distilled white vinegar and two-thirds water. Run this through the automated Self Clean. Let it cool a while, and then run another cycle using just water. Ideally do this every month or two depending on how often you use the machine.