Came across this app, "WeTap", which is a project of the Pacific Institute, in conjunction with Google Maps, to identify the location of public sources for drinking water. It is a fairly recent release, available for Android phones, and somewhat useless at this stage. But the concept seems good. With more people participating to identify the location of public water fountains nationally, a data base of public water sources with current operation, GPS coordinates, location photos, and Google Map position could provide a beneficial source of information available on your phone. Give it a try.
Currently the coastal cities in the Kingdom of Saudi Arabia gets most of their drinking water from desalination of sea water. That can't be cheap. (I used to work for a company that made RO water purifying equipment, and the Arabs were one of the biggest customers.)
Been using it for about a month without any significant problems. Having to log in to see locations, or insert a new location, is a bit burdensome, but I'm guessing to preserve the efficacy of the information, probably a necessity.
Got water at Monte Cristo campground on Angeles Forest HWY today after asking the ranger if it was good. It's just north on Upper Big T on AF HWY. Good to know since Hidden Springs cafe has been gone I did not know of any water supply anywhere along Big T
I can see something like that being useful in the mountains and deserts. Usually San Diego tap water tastes so bad I get water from the machines. Up in the Cuyamacas here, the water tastes like mountain spring water, probably because it is.