I have a 5 gallon waterer for the ducks and the chickens at night--it gets cleaned and filled every 2 days.(they empty it) during the day they drink from a pot with water or the pond. I have a one gallon for 9 chicks that are 7 weeks old, they go thru that every 2 to 3 days.
When I had 12 it seem to go about a week till it need to be filled However I often had to clean the water in the drinking ring. The amount of time it takes for that to get dirty varies with where it is.