The following photos show extremely dirty water left for horses that Steve shoes on separate properties. The second photo shows horse feces floating in it. If you can't drink the water left for your horse then your horse can't drink it. Cleaning the water source weekly by dumping old water and cleaning the receptacle with bleach prevents colic from dehydration and reduces the chance of West Nile virus.

Debris, hair and uncleaned water.

Horse feces floating in water source