The sequel
Thursday morning, we had no hot water in the bathroom. Plenty of cold, but move the faucet to the hot side, and it trickled, then stopped. Hot water, however, is served as usual in the kitchen. Conclusion, based on these facts: the hot water pipe (but not the cold) is frozen somewhere between the fork in the bedroom closet which splits the kitchen/laundry supply from the bathroom supply.
This is a bit of a surprise, because while cold (and quite icy—the landlord spread a full bag of rock salt on the sidewalk on Thursday), it has been colder around here this winter.
When I got home from the University on Thursday afternoon, the landlord was waiting, and shortly afterward, two plumbers showed up with a contraption that looked like a small jet engine. Plugged in, it generated some smoke and significant noise, scared the daylights out of Iz (which was good, because the apartment door was standing open), and directed a stream of heat at various walls they suspected of harboring frozen pipes. Eventually, they stripped the fixture off the shower pipes, so we could feel how cold that pipe was as opposed to how hot the pipe in our closet was, but their heater contraption was only heating the bathroom tiles (and the air—I saw 78 on the thermostat, which is usually set somewhat lower.) Eventually they gave up and went home.
The landlord, who used to live in this unit, thinks the culprit is the wind; it can get plenty cold, but if the wind is coming from a certain direction that chills the pipes more easily. He says it happened at least once when he was here as well.
Friday morning, they all returned, this time with a much smaller box with what looked like jumper cables attached. They hooked one contact on just above the split in the closet, the second behind the shower faucet, plugged in to a wall socket, and turned it on. Five minutes later, running water in the bathroom; the pipes had been frozen but hadn’t burst, and we were good to go. Plumbers departed, to be replaced a few minutes later by contractors who opened up the wall on the other side of the shower and put insulation on the pipes in hopes of preventing another freeze.
No problems over the weekend; we’re OK on water Sunday night. We get email from the landlord: “It’s going to be unusually cold and windy on Monday/night. Just to be on the safe side, could you let the hot water drip slightly.” OK, no problem, Monday night.
Monday morning, 8°F and windy: Just a trickle from the hot water taps. We’re too late. Still, this is a trickle, not a stop. I have the taps open hoping we can draw heated water up into the pipes and thaw the block without calling the professionals.
Evening update: We called the professionals. The water is thawed and now trickling.