I wasn't endorsing bottled water by warning against tap water, by the way. I'm aware that 40% of brands are just bottled tap water.
Hopefully this makes my stance more clear (from historyofwaterfilters.com):
"The threat of harmful contaminants in drinking water can no longer be reasonably ignored. The correlation between contaminated drinking water and many significant diseases and health problems is far too strong to discount.
Of course, municipal water treatment facilities have lowered the presence of many of the more harmful contaminants, and the
EPA has set maximum contaminant levels,
below which it is assumed that contaminants may be safely ingested into the body. Municipal treatments facilities are not infallible,
and EPA levels do not represent a safety level for every person. Children, the elderly, and those individuals who already have weakened immune systems, are particularly at risk to drinking water contaminants.
Two of the most volatile drinking water contaminants, chlorine and fluoride, are actually treatment additives. Also,
lead, another of the more harmful contaminants, enters drinking water after treatment and cannot be regulated by municipal water systems. Therefore, municipal water systems cannot and should not be trusted to provide healthy, clean drinking water."