Thanks Flyfish Dog! We're happy all this transpired in the unfinished half of the basement, and that we were home each time. It's an older house, built around 1950, and was pretty nicely put together, but one of the past owners suffered under the delusion that he could save money by doing things he had no business doing. We find them occasionally and shake our heads, but usually they don't cause us this much trouble. In the meantime, I'm considering having a cut-off valve put in next to the front door in the living room...last one out, please turn off the water.