1. A dog with a diet that consists mostly of dry food requires more water than a dog whose diet is comprised of wet or raw food.
2. Dogs prefer cold water.
3. Snow is not a suitable supplement to water. Ditto for salt water.
4. A healthy (but not overzealous) appetite for water can be an indicator of health, as it is directly related to kidney wellness.
5. Dogs drink out of the toilet because: the porcelain naturally cools the water, the flushing keeps water “fresh” (so to speak) and oxygenated, and the water’s relatively clean. Note: We do not recommend this. The toilet can be filled with both bacteria and toxins from cleaning solutions.
Sources:
http://ezinearticles.com/?7-Facts-About-Drinking-Water-for-Dogs&id=845422
http://www.ehow.com/how_4595450_dog-cat-drink-water.html