Essentially what it does is provides large volumes of water out of the provided pipes from the city water supply for people to fill up, for example, water tanks. man_made=water_well doesn’t exactly fit as it’s not a well. Officially, they are called “Bulk Fill Water Stations”, but I’m not sure how that would translate to OpenStreetMap tags.
man_made=water_point seems like a good fit for the feature on the whole, but I would also like to tag the specific connections. For example, this particular pumping station has 3 separate connections (depending on the volume of water that is desired):
(the last one is just a generic outlet without any intended coupling method)
I thought maybe man_made=water_tap but that doesn’t seem to be intended to be used with, at least, the first two. Furthermore, it doesn’t provide any established method for specifying a coupling type, or flow rate, or anything like that.