I recommend the documentary Water
I tells of the new research about water and how water has memory- as homeopathy has know for a long time.
Also, it says- if a dog gets the choice of tap water or spring /natural water- it will always choose the springwater....
I am searching for the link.. Will get back to you once I find it :)
My mom told me that one of her coworkers said she took her dog out on a rowboat in a lake and the dog got thirsty so she gave him some of her bottled water and ever since that he would not drink tap water only bottled water. If she gave him tap water or would put tap water in bottles to trick him he would not drink it and he would sit by the fridge and scratch at the door for bottled water.