In our house, the hot water heater dwells in its own partitioned-off room in the basement, with only the well pump and water softener equipment for company. That is to say, unless you have some specific reason to go into that area, you generally don't. A door separates it from Petunia's side of the basement playroom, and generally there is so much little-girl stuff in front of the door that you can't easily get to it even if you want to, but I digress.
Must be a dozen years ago now, since Thing One was a toddler and absolutely obsessed with the magnetic letters on our refrigerator at the time, I was constantly hearing a high-pitched mechanical noise in the kitchen and it was making me insane since I could not for the life of me figure out where the HELL it was coming from. Our basement stairs open into the kitchen near the refrigerator, so in a moment of extreme frustration I actually went down into the mechanical room in the basement, stuck my head behind the water heater in the course of examining it for the source of the noise, and thereby noticed that the water heater was leaking a little *before* it had a chance to totally flood my basement. Hallelujah. And the noise? Turned out to be coming from the battery-operated magnetic letter reader that went with the magnetic letters on the fridge, I discovered later.
Two days ago, I went down to the mechanical room to make sure there was enough softener salt in the container that goes with the water softener. This is something I do maybe once every six weeks. Damned if the water heater wasn't leaking again, but again just a little. Very happy to report that it was replaced with a brand-spanking new one this morning! Whew.