Our water heater broke sometime Monday, and we found out the analog way: Only cold water came out of the tap.

A visit to the basement revealed that the heater had already been reporting a problem in the least intuitive way possible. A single green LED on an assembly near its base was blinking out a pattern–eight flashes in a row, followed by a pause of a few seconds and then two more flashes.

That sequence, a small sticker explained, was the heater’s way of saying “Temperature sensor fault detected.” This same sticker listed 17 other sequences of flashes and pauses that could report anything from “No faults” to “Flammable vapor sensor fault detected.”

(The temperature sensor had indeed gone bad, although it took multiple visits by techs to confirm that and then return with a working replacement. This has left me with a renewed appreciation for household modern conveniences.)

That’s an awful user interface. It’s also what happens when you supply a single, single-color LED to display the status of a fairly complex home appliance. Bradford White, the manufacturer, could have put in a light that changed color–seeing a once-green indicator turn to red is usually your tip that something’s changed for the worse–or put in two or more LEDs.

Or that firm could have splurged on a digital readout capable of showing numeric error codes, bringing the discoverability of this interface up to that of the “DSKY” control of the Apollo Guidance Computer that NASA astronauts sometimes struggled to decipher on their way to the Moon.

Instead, sticking with that sole green LED and offloading the work of discovering its Morse-code-esque interface to customers may have saved Bradford White a dime per heater. On the upside, I’m now pretty sure I’ve seen the worst possible UI. I mean, not even Lotus Notes got this bad.