If you ever wonder if there is a real risk of bottled water being replaced by tap water, there may be no better source of information than the annual report of American Water Works (stock symbol AWK).
AWK is the largest publicly traded tap water company, and I think most Americans don't understand there is a growing privatization of tap water systems in the US. From AWK's 10K report you can get an honest reading of the looming costs to tap water infrastructure as well as "risk factors" in the tap water business. Unfortunately, they don't disclose quality problems as they consider that merely "regulatory matters in the normal course of business."
"The aging water and wastewater infrastructure in the United States is in constant need of modernization and facilities replacement. Increased regulations to improve water quality and the management of wastewater discharges, which began with passage of the Clean Water Act in 1972 and the Safe Drinking Water Act in 1974, have been among the primary drivers of the need for modernization. The EPA estimates that approximately $335 billion of capital spending will be necessary between 2007 and 2026 to replace aging infrastructure and to comply with quality standards to ensure quality water systems across the United States. In addition, the EPA estimates that approximately $390 billion of capital spending will be necessary over the next 20 years to replace aging infrastructure and ensure quality wastewater systems across the United States."