Most bottled water is sold by private companies and because tap water must be checked daily under a rigorous inspection regime, and bottled makers are only required to undertake monthly testing at the source, bottled water can actually be significantly worse, the study found.
The study reported that tap water also contains trace amounts of chlorine that prevent the spread of anything harmful such as bacterial infections. In contrast, a bottle of water might remain in storage for months after being bottled before it is sold and few contain any disinfecting additives such as chlorine.
In addition to these findings, there's also the significantly higher cost of bottled water. It can cost up to 1,000 times more over time.
"People think there must be something wrong with tap water because it is so cheap and plentiful. But from a safety and price perspective, tap water is better for you," said Prof Paul Younger, of Glasgow University. "If the bottle is accidentally opened or someone tampers with it, then it can easily get contaminated."
Younger, who is the author of the book "Water: All That Matters," also told the Daily Mail, "There's certainly a greater chance you could find something harmful in bottled water than from your taps.
"Ideally it should be drunk on the day it is opened, as it can easily pick up bacteria from someone's hands or face."
Market researchers Mintel have found that almost a quarter of people who drink bottled water at home say they do so because they believe it is "better for them" than tap water.