The old heater didn't drain very quickly, so they removed it while still half-full... took it out by way of the basement side-door and decided to drain it there in the stairwell, where there's a drain.
The drain clogged up. Next thing I knew, one corner of my basement nearest the door was full of dirty-black water. Eeeeew. I about snapped and killed both guys right then and there, even as I rescued books from the bottom shelves of the bookcases...
Eventually, the new heater was installed. Then they set off the smoke detector while soldering the pipes into place. THAT woke my dearest wife up out of a sound sleep, even as we practically ripped the detector out of the ceiling trying to turn it out.
After that, we finally managed to get the drain to declog and got the water out. Ugh. NOT the mopping I had in mind. They brought in a wet/dry vac to get the rest of the water that had leaked from the mess, and all was well in the end.
So, problem solved. In a typically messed-up manner. Oy. I tell you, if there's a way water can get into my basement, it does. On the bright side, I've started really cleaning the basement... :>