I'm not sure if there are any risks but I try to make sure the girls have fresh water daily and clean out their drinkers at least once a week. However, every time I water the plant pots or spill any other water in the garden they go absolutely nuts and crowd around to sip up every last spot, supping from the top of the plantpots as the water is absorbed, almost licking the paving or ground to get every last drop. They also drink from anything that is left around no matter how gross it looks and how many things are floating in it.
I guess no one has told them that they should drink fresh water.
My black lab also prefers dirty water to anything out of the tap.