I would let him drink as much as he wants. Puppies and dogs drink lots of water, it's good for them (as long as they are drinking fresh, clean, filtered water). If you want you can take it away late at night before bed, but remember to put it back first thing in the morning. If he's drinking it so fast that he's throwing it up, you can try putting in ice cubes to try and slow him down. Just make sure he doesn't choke on them.