Most dogs don't have a good sense of portion control when it comes to food, so offering food only two or three times a day is a smart idea. Water, on the other hand, is something he can't overindulge in, and it should be available any time he wants it.
Hydration
It's just as important for your pooch to stay hydrated as it is for you. Not only will it keep him feeling good, but it's vital for his circulation, digestion and temperature regulation. Dehydration can lead to kidney damage and heart problems, as well as heat stroke in the summer. With few exceptions, your dog should have constant access to water and be allowed to drink as much water as he wants so that he will stay hydrated.
Safety
Place water bowls that are left down all day where the dog can get to them easily, but babies and toddlers cannot. A young child can actually drown in a shallow bowl of water, especially if she slips and falls face-first into the bowl or aspirates some water into her lungs. In addition, water bowls in constant use can be a hotbed for germs, bacteria and algae. Make sure your dog's water is safe for him to drink by cleaning the bowl regularly and emptying and replacing all the water at least once per day.
Housebreaking
Keeping a regular schedule is one of the keys to housebreaking a dog. It is one of the few times when it might be necessary to pick up the water dish and provide water at regular intervals. It's still important to make sure your pup is getting plenty of water, even if it means more trips outside. Let your dog drink as much as he wants each time you offer the water bowl, and then take him outside. Young puppies process water quickly and will usually pee within a minute or two of taking a long drink.
Other Considerations
Your veterinarian may advise you to restrict your dog's water under certain conditions. For example, several hours before your dog has surgery, you may need to remove his water bowl. Dogs with profuse vomiting might also be temporarily restricted from consuming anything by mouth, including water, to get the vomiting under control. Do this with caution and only under the guidance of a veterinarian so that your dog does not become dangerously dehydrated. If your vet asks you to restrict or monitor your dog's water intake, watch for and report any signs of dehydration, such as sluggishness, a dry mouth, loss of appetite and depression.