My dogs (2 boys 7 and 1) also each have their own food and water bowls. I keep dry food out for them all day and then when I "feed" them, put wet/dry together. When I feed them they will eat out of their own bowl. During the day, they'll only eat the dry food out of the older one's bowl. The younger one will take a mouthful and come into the dining room, which is carpeted, and drop the food then eat it. The older one will try to "sneak" wet food out of the younger's bowl if he leaves some in there. They will ONLY drink out of the older one's bowl, even if it's empty and the other bowl is full. If I move the bowl to the other spot, they'll drink out of it. Go figure!
To add, when we got the puppy last year, he started drinking out of Bailey's bowl and I heard this yelp. I looked into the kitchen and Bailey had this completely SCANDALIZED look on his face, like "hey mom get this dog out of my bowl!" Later that night when we were going to bed, Bailey kept acting like he had to go out. I went downstairs and opened the door and he just stood there. I, the stupid human, finally put two and two together, emptied out his water bowl, rinsed it, and filled it back up. He started drinking like he hadn't ever drank before. He mustn't have touched his water all day! Poor guy. They've since adjusted.