Does the water get funky or stagnant if they don't drink it fast enough? I only have 6 hens so looks like this company sells a two gallon premade that may be big enough. Don't want five gallons or more sitting around and getting old. I'm cleaning out the duck pool every other day so filling not an issue.
My 5 gallon waterer is in my coop and I haven't cleaned it out in 8 weeks. No slime or build up, I just add fresh water once a week for 8 hens. When I was using the 1 gallon waterer in my brooder, I didn't clean that for 5 weeks and never had an issue either. Now if your waterer is in direct sun, it may have to be washed out periodically, plus the water would get hotter, than being in the shade.