Tap water in Finland is much purer than many brands of bottled water. A report by the Finnish National Public Health Institute claims that bottled water (13 Finnish brands and 5 foreign brands) contained as much as 100 times more germs than regular tap water.
The explanation is that with bottled water, there’s an “expiration date” as the longer water sits in a bottle, the more likely it’s going to get contaminated with microbes. Mineral water can help with the purity–the bicarbonates in it inhibit bacteria.
I wonder how Finnish tap water compares with Fiji water, which several publications have revealed is extremely damaging to the environment to produce and transport. I think this goes to show that in when you’re traveling in a first-world country, forget about the bottled water. It might just turn out to be good for your health too.