This morning my wife and kids took showers upstairs just fine. My daughter wanted to take a bath in our bathroom hot tub, since our furnace is out (we live in Washington state) and are awaiting a new circuit board, the water wouldn't get warm. The remaining faucets upstairs are running cold when turned on hot. Downstairs faucets, kitchen, bath and laundry room are still providing hot water. We have single Rheem gas hot water heater in the garage. As I just checked it again, it appears to be leaking water very slowly from the top. It is New Year's Day, so getting plumber before Monday might be impossible. Ideas?

Do you have a hot water re-circulation line?
Does the water heater burner come on when water is used?

Actually, it seems to be working fine now, I'm not sure why. This is the first time in the nearly 8 years I've lived her that it happened.