As a follow up to the "distilled water" thread I found this article that I thought was good. This topic related to dogs seems to be hardly mentioned in any scientific articles that I've found. I know it seems to be somewhat of a consensus that certain waters (and I think more so foods) can be the source of eye stains. And it does seem that distilled water can help with the eye staining, but I'd like to know whether distilled is the best choice in general say over spring water which theoretically would contain important nutrients.??? I'd like to research this more and if anyone has more information, please share. But this article is good and the one point that I tended to agree with is, the fact that water should always be accessible, because some people will restrict it when house training young pups, and I don't think that's advisable. Here's the article anyway. http://www.dogfoodadvisor.com/canine-nutrition/water-most-neglected-canine-nutrient/