Water water everywhere

I went to a kids indoor play area today that had an integral cafe.

There was a strange sign near the cafe menus. To paraphrase, it stated that they are constantly asked for tap water. They wanted to advise customers that they are not required to provide tap water and that they sell bottled mineral water in two bottle sizes.

I thought this was bizarre.

It is an establishment that caters for children. I know that for very young children that the advice is to give them tap water in preference to mineral water because the latter contains minerals in concentrations that aren't ideal. The same government advice would promote water over squash or fruit juice. It also stresses that it's important to ensure children remain hydrated and these are places where kids expend a lot of energy and get hot and need to maintain liquid levels. So, although tap water is better for children, they choose to deny parents this choice.

I also thought that there was an obligation requiring catering establishments to provide tap water when requested. Maybe I'm wrong.