I have already weaned him from the replacement kitten milk by slowly introducing cat food mixed with the replacement milk for about 5 days. Now he is fully on cat canned food. I haven't noticed him drinking any of his water though. Should I be worried. I put a small amount in a bowl next to his food a week ago and it doesn't look like he has drank any of it. What should I do?

You need to keep him on the kitten milk. Kittens aren't weaned by their mother until they are at least 8-10 weeks old, and often still nurse for a time after that. He still needs the nutrients in the milk. You can put the kitten milk in the bowl, instead of a bottle.

If you want to have a bowl of water out, then you need to change the water at LEAST once a day. Most will not drink old or dirty water.

No matter what you do, you NEED to make sure he's drinking something. It takes VERY little time for kittens to become dehydrated, and die. Even if you end up having to bottle feed him a couple times a day, he HAS to drink something (preferably kitten milk, at least part of the time).