You may think you're making life easier for your cat by using a double dish for food and water but some cats don't like water so close to their meal. In between meals when a cat goes for some water she may not want the smell of food nearby. Food particles that spill into the water can also contaminate it. If you feed dry food and some water spills into it, that can make the food less palatable. If you use separate dishes you're also more inclined to keep the bowls cleaner. With a double feeder that still contains dry food you may just refill the water side without washing it. If you're concerned about your cat not drinking enough, try using a separate water dish and place it away from the food bowl.
Pam Johnson-Bennett, CABC, is a certified cat behavior consultant and author of seven best-selling books on cat behavior. Her website is www.catbehaviorassociates.com.
Just a little note, I didn't write this tip, I am just sharing it :)