
Hi,
This is the normal reaction of a pup - he's just so excited, and a little nervous and submissive too, that he wets himself. Please, take no notice of this. Don't scold him because he's not doing it on purpose - he probably isn't even aware it happens.
I've had several pups do this and they all grew out of it as they became more mature and confident. If he does it when you come home, greet him where a puddle doesn't matter. With ours we used to open the back door and call the puppy outside to greet her.....so what if she puddled!
The quickest way to stop it, in my experience, is to do nothing! As he grows up he will grow out of it. So please don't make a big deal of it or you may make him nervous and it will go on longer.
Hope this helps :)