This instructable stems from my being lazy and my very large dog that drinks lots of water. I doubt this idea would scale down for a small dog but it works great for for 5 gal buckets. The photos i have taken are actually from disassembling and cleaning a water bowl that i have used for over 3 years. This is a pretty simple build.
Galvanized tub (about 5 gal)
Diaphragm style toilet bowl filler
12" toilet bowl supply line
brass garden hose female fitting with 1/2 male barb
1/2 to 3/4 inch hose clamp
Power drill and 7/8 bit