I have always kept a strict schedule with my waterers, once a week they are soaked in a mild bleach and water solution, they are changed every day once in the morning and once at night. I use the gallon size waterers and because I have well water it leaves an orange film in them if I don't do it once a week. If they are caked with poo I scrub them immediately. I have a pair of call ducks too who live with the chickens and boy oh boy do they make a mess of the waterers. I think I have 5 total out there plus a dog bowl of water inside a tub for the ducks but they prefer to use the chicken waterers instead and use theirs to sit in