General Information :
Automatic drip coffee makers will accumulate hard water deposits along the lines and in itâ€™s tank.
Tools & Technique :
Every month or so, brew a solution of vinegar and water to remove the deposits.
Also clean the filter, baskets and carafe after every use. Most can be placed in the dishwasher, never use abrasives on your coffee makers surface or the heating element. If you do not have a dishwasher use dish soap and water just like washing normal dishes. Residue and bitter oils on these surfaces will affect the taste of the coffee.
Pour 2 cups of white vinegar into the pot and fill will to the 10 cup level (1:4 vinegar to water). Pour the solution into the reservoir place a fresh paper filter or your multiple use filter in the basket and brew about 50% of the solution stop the brewing process for several minutes to loosen everything and continue to brew.
If you have heavy build up or have not cleaned the coffee maker in a long time pour the solution back into the reservoir and brew it again. Be sure to brew a cycle with just water to rinse it completely. And your next brew of coffee will taste like a fresh cup of Starbucks coffee.
There are also off the shelf products like CLR and lime away which will remove extremely stubborn stains.