I'm in Colombia, and recently visited lake Neusa - highly recommended, by the way!
The advice on drinking tap water in Colombia seems to be generally, big city/tourist hub = fine, otherwise avoid.
Despite this advice, I've still mostly avoided tap water in the cities, apart from brushing teeth. This is mostly due to an instinct of city = pollution = bad rather than anything evidence-based.
However, I noticed whilst up at lake Neusa that my instinct told me the opposite, that the water would be fine to drink. Being up in the mountains, next to a beautiful lake, it gives you a very strong intuition that everything's going to be clean, fresh, and OK. After all, images of mountain vistas are used heavily in marketing for bottled water, so it can't be just me!
Is there any basis in fact for this intuition? Are there any reasons, or evidence, that water up in the mountains is likely to be in any way safer and cleaner than that in towns and cities, given broadly similar water purification standards and technologies?
Off the top of my head I'm thinking it could simply be easier to clean in the first place due to being fresher and more quickly replenished, less exposed to pollution of various kinds, etc.