I'm confused your takeaway here. It definitely does have very "pop-science" data, throwing together whatever data is available in order to create an appealing product that seems to tell you something. The agenda is definitely more pro-environmental and anti-water bottle though. If they were trying to show a more neutral comparison of bottled cost to tap for a region, it wouldn't be phrased in terms of a savings.

For the map itself, Numbeo is not the primary source, that would be the WHO data, which is weighted 3 times more than the data coming from Numbeo to put an emphasis on a more reliable data source.

The cost-saving from not drinking bottled water is not necessarily dependent if the water is drinkable or not, as water filters are widely available and can offer substantial savings -> https://home.howstuffworks.com/save-money-with-water-filter1... The prices are taken from Numbeo and are the average prices for 1.5L bottles. I am aware this is not a perfect calculation method, I am planning to add a cost-saving calculator soon which will offer more flexibility.

Regarding the reputable source of information, you are right. Country-level data can never be a good decision-tool to chose if you can drink tapwater somewhere or not. It has to happen on an area-basis and include scientific reports, which are hard to get as of 2020 as there is no single source/database/API for that, except for very few countries (including the US and Austria), I'm working on that and I'll try to improve the UI so it reflects that one should check the water quality in the area of interest rather than the country itself.

IDK, for me it looks more like a taste map than a quality map. In Spain northern regions have almost perfect water where mediterranean regions do have taste and more problems due the nature of their sources of water. I mean, it's not very useful. You'd drink tap water in my city or Madrid, you wouldn't like it in Barcelona, although you can.

> Don't understand why you have a marketing type message that offers a calculation cost of savings from not drinking bottled water.

I thought that might also be prone to inaccuracies. For example, I live in North York (a burb of Toronto) in an area where our water is paid for in the taxes. So we'd probably save a whole lot more than the estimate by not drinking bottled water. Since it is part of our taxes, we would still be paying for the taps even if we opted for bottled water.

Not to disrespect any country, but the fact that Tunisia ranks higher than Italy it's a bit ridiculous...

Which country exactly would be disrespected in this case? :D

On a serious note, Italy indeed has some tap water problems https://en.wikipedia.org/wiki/Water_supply_and_sanitation_in... , although common sense and the internet telling me that I'd rather drink tap water in Italy than in Tunisia...

You clearly have never been to Belgium (and I’m sure other EU countries) where, who ever can afford it, only drinks filtered water, and typically water fountains in offices have cucumber or mint etc to give it a more palatable flavour. To say it’s the same water as in, ie Sweden is ludicrous.