reply to elanp
Re: Hot Water Runs Out Quickly: What's Wrong With My Water Heate You're misunderstanding how the hot water system works. You need the cold water ON in order to provide the pressure for the hot water to come out of the tank.
The only way to drain the tank with the cold water OFF (i.e. without refilling the tank) is to use the drain valve on the bottom of the tank.
Hopefully you have a functioning floor drain near the tank, and a length of garden hose to get from the tank to the drain. Open a nearby hot water faucet to let air back in to the system so it will drain faster.
I'm thinking you should call a plumber, though.