Changing opinions

During the course "The Science of Everyday Thinking" (a MOOC sponsored by edx.org and led by psychology professors at the University of Queensland, Australia), I learned the 6 leads of opinion change.
The video of the lecture about this topic is here: 6 leads of opinion change.

I will apply the 6 leads of opinion change to the question of this blog, tap water or bottled water?

1. What do you really believe anyway?  Things are rarely black or white, they say, although it would be tempting to see the world that way. I believe there are situations when tap water is okay to drink, and times when bottled water is a better choice. Neither is completely good or bad.
2. How well based is the opinion that you already hold? I have strong evidence from several reliable sources that tap water in Budapest - where I live - and in most European, UK, and North American cities, is clean and safe to drink. I also have evidence that the bottled water industry has marketed the idea that its products are preferable to tap water.
3. How good is the evidence? In the case of tap water, I have read about official tests of the public drinking water showing it is safe. In the case of bottled water, I need more evidence, because many conservation groups and water companies produce data that is tainted in a particular way. However, I don't think I should reject what the conservation groups and water companies say, yet.
4. Does the evidence really contradict what you already believe? This is a difficult question for me! I'm working on it. At the moment, the evidence agrees with my belief that Budapest tap water is potable.
5. Given the evidence, if that's not enough to change your mind, then what would be enough? I think I would need to see tests of the local drinking water showing it is very polluted and harmful to my health.
6. Is it worth finding out about, or is it just a case of why not? It's worth finding out more! That's because the landfills and gardens, public buildings and parks are full of discarded plastic bottles which take forever to break down. If people can be convinced to drink tap water whenever possible, our environment will be improved.