This morning all my hot water was out. (Cold shower = not such a problem when you're in a semitropical climate, it's still summer weather, and you've just worked out.) I checked the water heater and the circuit breaker and didn't see anything obvious to fix. So I waited until the Very Nice Apartment Guard came in, to ask him to check it (so many things are different in Taiwan: he's familiar with local systems and I'm not). The next step would have been to call the rental agent and ask him to get a plumber.

The VNAG found the problem. Was a breaker flipped? was a pilot light out? No, no: my hot water was out because the hot water heater's battery was dead. (boggle)

It's not as silly as it sounds: it runs on gas and apparently instead f an always-on pilot light, the battery powers an ignition system. But it sitll strikes me as funny.