[Tagging] drinkable vs. drinking_water

[Martin Koppenhoefer]

The general tag for a source of drinkable water is
amenity=drinking_water. But in some cases you will want to subtag an
existing OSM-object (like an amenity=fountain) with the info that the
water is drinkable.

Apparently our free tagging schema has led to 2 alternative keys for this:

drinkable=yes/no can be found here:
http://wiki.openstreetmap.org/wiki/Tag:amenity%3Dfountain

drinking_water=yes/no is defined here:
http://wiki.openstreetmap.org/wiki/Key:drinking_water

The first is around 5 times more in use than the second. How shall we
proceed in order to unify the two?

cheers,
Martin