Ok, I use a "hog pan" with a piece of plastic foundation propped on one side so the bees can land on it, and walk to the water. I rinse it out every so often, and they don't seem to mind. We also have a pond out there that I'm guessing they go to.
If you want to use Sodium Hypoclorite, Household bleach, to keep the water sterile, you wont need a lot at all. If you remember back to the boy scout training, you can sterilize a quart of water with 1 or 2 drops of bleach and wait 20 minutes. I use it in my Syrup. 4ml, or 4/5 a Teaspoon of bleach will keep a gallon sterile.
Since I usually make 2:1 syrup and store it, then dilute it, it will then be equivalent to 2 or less ml per.