I thought this subject could wait, but it is becoming pressing early than I expected. 

As part of our project (and that of similar non-profits - most of which are not open data but nevertheless great organisations), we want to voluntarily encourage cafés, bars and restaurants to offer free tap water bottle refill to anyone off the street.  Refill has had significant success in the UK and surprising the feedback is that the impact of increased customer traffic far outweighs any issue of cannibalization. 

If it is not already the case, I would like to work with you with on developing a tagging standard for this case which maybe we can vet in a wider OSM audience. Maybe "amenity = cafe & free_water = yes"

It would be important to develop at the same time a distinct tag for another cause, which we support but will not be targeting is restaurants which offer free tap water for paying customers.

Maybe "amenity = restuarant & free_carafe = yes"  

Many thanks,

Stuart