Good advice. I don’t know what waterer you are using, knowing that may help with specific suggestions, but in general try elevating the waterer to the height of their backs. That will help keep it cleaner from them scratching stuff into it and help reduce them pooping in it. Elevating a piece of plastic or plywood to form a platform above the bedding helps too, but they will scratch bedding up there so you need to clean that off occasionally. Put your waterer in the middle of this platform. Putting something over the waterer to stop them from perching on the waterer can really help reduce them pooping in it.
Dirty water, especially if it has poop in it, is a breeding ground for problems. Clean water is one of the best things you can give them. There are other potential problems but the bug that causes Coccidiosis thrives in warm poopy water. That’s a big risk. If you dump that dirty water out once a day you interrupt the life cycle of that bug, so to me that is a minimum, once a day if they are pooping in it.
Another problem with not dumping the water is that it can become a breeding ground for mosquitoes. If you dump that every couple of days you get rid of the wigglers before they mature. Some people use nipples or some other watering system to eliminate the potential problems of poop or trash in the water but may not think of the mosquito problem in their water tank. (I see CT responded while I was typing)
A wet brooder is a dangerous brooder the same as dirty water is dangerous. You need to do what you can to keep your brooder dry.
Good luck! It’s a good question.