Found a small pool of water at the base of my water heater Christmas eve and thought I'd have to buy a new water heater. That would have been a very expensive repair bill! Luckily, it turns out the leak is due to the inlet adapter pipes rusting out due to my water softener. I guess the salt that I used to use caused the galvanized pipe to leak. So water was being forced out through the pipe at the top as the tank filled up. I've been using potassium tablets instead of sodium for my softener now, but I guess the few years of using salt took it's toll already. Tough to find parts and plumbers during a holiday break like Christmas.
Update: Need to replace water heater due to internal tank corrosion. I'll need to make sure to inspect and/or replace the anode every 5 years or so to avoid this problem in the future.