Nearly all of the water (99%) that comes out of municipal taps is used for general purposes, such as watering lawns, washing clothes, disposing of waste, fighting fires and so on. Less than 1% is used for consumption in food and beverages. The Safe Drinking Water Act requires the public water systems to comply with health standards, monitoring and reporting requirements. The U.S. EPA, individual states and local municipalities work together to meet these standards with consistency. But since so much water is used for non-consuming purposes (e.g., flushing toilets), it is economically infeasible for local municipalities to use treatments in their water systems that produce a high-grade drinking water that has ideal flavor.
The qualify as safe drinking water, water must be clear, odorless and tasteless. It must be free of bacteria and contain less than 0.2 mg/L of copper, 0.3 mg/L of iron, 250 mg/L of sulfates, 250 mg/L of chlorides, 100 mg/L of magnesium, and 1,000 mg/L of total dissolved solids. The water standards also specify it can contain no more than 10 mg/L alkalinity (with no caustic alkalinity) and less than 50 mg/L of sodium or potassium alkalinity.
And while these standards may be acceptable for general use, they do not necessarily make the best coffee. Municipal water carries tastes and odors than can become objectionable when used for food or beverage preparation. Further, certain substances that naturally occur in water have an effect on the brewing process.
