Us at 734 Coffee love to make a great cup of joe, and one of the things we consider is the water used.
You can ruin a great cup of coffee by using water that has additives. The quality of the water you use is another often overlooked aspect of brewing coffee. Using tap water that's full of minerals or chlorine won't bond well with the dissolved particulates from the coffee, leading to an under-extracted, weak coffee. Not only that, this higher mineral content is what also leads to buildups in your coffee maker, such as lime deposits. This will require you to descale your coffee maker more often.
On the other hand, using heavily filtered or distilled water can be just as destructive for your equipment. While it doesn't cause as much buildup, Seattle Coffee Gear explains that its lack of ions and mineral content will force the water to "leach minerals out of the metal components and degrade the machine's performance over time." Plus, with more room for bonds, distilled water can easily lead to over-extraction.
We suggest you use water that's roughly in the middle of the spectrum, with a mineral balance of approximately 150 parts per million. Ideally, use bottled spring water or activated-charcoal/carbon filters on their taps. However, if you, not a coffee snob but a casual drinker using lightly filtered water (from a water filter pitcher or a refrigerator's filtered water) will work too.