advice on a DIY water top off system

[hillbillyreefer]

I've used one of the little giant floats for years in the horse pasture, hasn't failed yet. It's just bolted to the trough, unprotected from the animals. They work well is what I'm saying. I'm sure I got mine at UFA that's about the only place around here to buy stuff like that. Gallagher also makes a similar float, I have no experience with it though.