KitchenAid ® does not recommend distilled water because of issues with the flow rate through the coffee grounds.
- Because distilled water is such a good solvent, it causes the coffee grounds to swell and slows the flow of water. This leads to bitter, overextracted coffee or possible brew basket overflow. It is even worse with decaffeinated coffee.
- Distilled water also causes the metal brewing element to slowly deteriorate the hot water tube, causing premature failure of the coffee maker.