This Device Monitors a Wonky Toilet's Reservoir Status

Few things in life are more irritating than a malfunctioning toilet. You've experienced this anytime you've entered a friend's bathroom and received the advice to "just jiggle the handle." From a mechanical point of view, toilets are actually quite simple. But they can falter if the fill valve or flush valve start to stick. If the fill valve sticks, you end up with an empty tank and the toilet can't flush. If the flush valve sticks, water keeps flowing endlessly. To notify residents when that occurs, Jacob Preston designed this ToiletMonitor.

The ToiletMonitor has one job: to sound an alarm if the toilet reservoir does not refill after a flush. It can't actually do anything about that problem on its own, but the alarm will hopefully get the attention of bathroom-goers while they're still washing their hands so they can come back over to give the handle a jiggle.

This requires surprisingly little hardware. The primary component is a SparkFun SAMD21 Mini Breakout board, which is a small development board that takes advantage of the fantastic ATSAMD21G18 microcontroller. It is a bit overkill for this project, but is still affordable. Three other components connect to that board: a button, a piezo buzzer, and a USB breakout. The microcontroller drives the piezo buzzer through an NPN transistor with power coming from the USB breakout. The button turns off the alarm.

The ToiletMonitor is able to detect the water in the tank through a pair of wires. When they're immersed in water, some current can flow between them. When they're out of the water, the resistance of the air stops all current flow. The user just has to position the wires so they're immersed when the tank is full, but not immediately after a flush.

The rest is just some clever programming. The ToiletMonitor starts a timer when it first detects a lack of immersion, indicating that a flush just occurred. If it doesn't detect immersion again within a reasonable amount of time, it knows that there is a problem and it sounds the alarm.

This is probably more work than simply fixing the toilet. But it keeps the Preston's toilet from running continuously and overfilling their septic tank, so it solves a real problem.