Essentially, the water is overflowing... it's a steady trickle coming from the bottom of the top console (the hot water one). And I've shut off the power to the heater so it's not heating. I turned off the obvious knob at the top that looked very much like a water shutoff valve. And despite constant efforts to run the faucets, wipe up the water, stick something absorbent in the water, and use the pressure valve to drain some water, it just keeps building up again and leaking.
I know about the part where I get a hose and empty the tank via the draincock at the bottom. No hose immediately handy, this must wait until decent hours. I'll be calling a professional as soon as possible in the morning. In the meantime, if anyone has any advice, suggestions, experience, feel free to chime in.
Sigh. Always with the flooding in the basement. If it's not one thing, it's another.