Thanks once again for all the info, everyone.
Update: I've cut/torn out as much carpet and underlay as I could from
around the heater, and I should be able to 'tip' the heater enough
(with the assistance of a friend) tomorrow to get the remainder of the
junk out from underneath it. The heater will then be sitting on the
concrete foundation - which should make the tracking of water leaks
After running a dishwasher load and washing machine load at the same
time, it doesn't appear the T&P relief valve is letting go after all.
There was nothing in the jug I placed below the drain tube.
So...now I'm wondering just where the water may have came from. My
wife (who is short on technical knowledge but pretty good in the
common sense department) suggested the heavy rainstorm we had a few
days ago might've had something to do with it. Of course, the
foundation is behind drywall...
I went so far as to remove the two access plates for the thermostats/
elements. No apparent signs of leakage, nor are there any signs of
corrosion at all. The tank looks new.
I've currently got a dehumidifier stuck in the closet where the water
heater is. I'll let it dry out nicely, get the remainder of the
carpet and underlay out of there tomorrow, and then play the waiting
game to see if water reappears. We've got a rain-free forecast for
the next 5 days, so if anything appears near the water heater, it'll
have to be coming from the tank.
I hate this crap. Give me a radar to fix anyday.