Vicki,
Regarding the waterer, I like the looks of the picture. As far as knowing how long they will go, I am finding my runners difficult to predict. We went from a quart, to two quarts, to a gallon, and now have a three gallon waterer, which is my limit because full it weighs around 25 pounds - about what I can comfortably carry at my "advanced" age
Here is the trick: Since they were about six weeks old, and had started the bad habit of apparently splashing out every drop of the three gallons overnight (standing water in the brooder, oh yeah!
), I went with Storey's advice that they can do without water just fine for 8 to 10 hours. So, for about 5 to 8 hours, they don't have water or feed in the brooder, so I don't have to destroy a wetland every morning.
Now then. Some mornings, they go through a couple of gallons in an hour. Some mornings, there is still a gallon of water left after five hours (from the time I give them water in the morning to their morning brooder change). It depends. They seem to drink less when they are more settled, which is within 48 hours after spending an afternoon outdoors, where I can provide drinking water and swimming water.
I hope that pile of data helps you somehow. Perhaps one nugget is that after six weeks, running out of water is much less of a big deal than right now with your calls. I used to get so edgy if I had to leave the house for more than two hours. Now it is no big deal. If I leave them with three gallons, they will be fine for a few hours even if they splash it all out.
Last time they were at all consistent with water usage, they were getting about three hours on a gallon. They are runners, adult weight about 3.5 pounds, if that might help you make a guess.