What about the water temperature? If it is about 100F air temperature, it won't be long before the water in a 5 gallon bucket is 100F. Chickens won't drink hot water. frozen water bottles dropped in the bucket or fount a couple times a day will help.
I use large rubber feed tubs with a frozen water bottle floating in them for foot baths that some birds will take advantage of.
I can open the top of my 5 gallon waterer and add fresh cold well water , I do this every morning and check them in the afternoon.
I like the frozen water bottle idea, I’ll add that to my birds kitty litter pools thanks