First off, if your Bassett Hound drinks a lot of water, he's going to urinate a lot more because of it! :P Just like if you drink a lot of water, you have to use the bathroom more often too. And 2 gallons of water a day isn't bad for a Bassett Hound especially if he's unusually active for a Bassett. I wouldn't worry about it too much right now if I were you. Like I said, 2 gallons isn't a whole lot more over normal.
When dogs get older they seem to drink more water. We are going through this now with ours - just signs of old age. :) If you are concerned though call your vet - some will give you advice over the phone. Or look up a local Bassett Hound rescue in your area - rescue groups who specialize in a certain breed are usually well informed and can answer any questions you might have.
In case you aren't aware of it, dogs can be diabetic just as humans can. I'm by no means telling you that your dog is diabetic, but you really should take him to a vet, because excessive drinking and urination are a couple of the symptoms of diabetes.
I switched my basset (13 years old) to canned dog food and it seemed to fix his problem.