---
title: My Leak Sensor Lives in the Shower
description: I put a leak sensor inside the shower to detect showers. A 90-minute wet-recently flag keeps a pad that stays wet from holding the bathroom lights on.
image: https://willcurran.com/hubfs/will-curran-brand/my-leak-sensor-lives-in-the-shower-featured.png
---

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# My Leak Sensor Lives in the Shower

I put a leak sensor's moisture pad inside the shower on purpose, as a shower detector. Because a wet pad can stay wet, the logic that holds my bathroom lights on reads a flag that turns on at the dry-to-wet edge and turns itself off after 90 minutes.

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Will Curran Nov 13, 2026 · 2 min read

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![An abstract dark scene: falling orange droplets above a flat moisture pad, with a ring-shaped timer three-quarters closed, next to the title My leak sensor lives in the shower.](https://willcurran.com/hs-fs/hubfs/will-curran-brand/my-leak-sensor-lives-in-the-shower-featured.png?width=1600&height=900&name=my-leak-sensor-lives-in-the-shower-featured.png)

I put a leak sensor inside a shower, on purpose. It's a small moisture pad, the kind sold to tell you water has reached the floor. In a shower it gets wet when someone showers, and that's the job I gave it.

The catch is that a wet pad can stay wet. So the logic that holds my bathroom lights on reads a separate *wet recently* flag, and that flag turns itself off after 90 minutes.

## A stuck pad looks like a shower that never ends

A leak sensor reports wet or dry. It has no idea whether the water is still running, so a pad that stays wet looks exactly like someone still in the shower.

An earlier version of my lights logic read the pad as-is, and while the pad read wet it kept the bathroom lights on. The first fix pulled the pad out entirely.

## Count the edge, then let it expire

The flag is a trigger-based template sensor in Home Assistant, with three rules:

- **It turns on only when the pad goes from dry to wet.** A pad that comes back online already wet doesn't count.
- **It turns off when the pad dries.**
- **It turns off by itself after 90 minutes**, wet or not.

![Timeline diagram with synthetic times, in two cases. In the first, the pad goes from dry to wet and stays wet; the wet-recently flag turns on at that edge and turns itself off at 90 minutes even though the pad is still wet. In the second, the pad dries before 90 minutes and the flag turns off at the same moment. In both cases the flag turning off fires a re-arm check of the bathroom lights.](https://willcurran.com/hs-fs/hubfs/will-curran-brand/my-leak-sensor-lives-in-the-shower-wet-recently.png?width=1440&height=1000&name=my-leak-sensor-lives-in-the-shower-wet-recently.png)

## One vote among four

When an automation turns lights off around the house, any one of four signals can spare the bathroom: motion, a shower sensor built from humidity and water flow, high humidity on its own, or the wet-recently flag.

A veto needs a way to undo itself, which I wrote about in [The Veto That Never Retries](https://willcurran.com/blog/the-veto-that-never-retries). So the flag turning off is a trigger too.

## If you are about to try this

- **Trigger on the edge, not the state,** for any sensor that can stick.
- **Give every "recently" flag an expiry** longer than the thing it covers.

Give this to your AIHelp me use a water leak sensor inside my shower as a shower detector in \[automation system\]. Don't use the pad's state directly. Build a wet-recently flag that turns on only when the pad changes from dry to wet (ignore it coming back online already wet), turns off when the pad dries, and turns off by itself after \[minutes, longer than a long shower\]. Make the flag one of the signals that keeps the bathroom lights on, with a re-arm trigger that checks the lights again when it turns off. Include a test that holds a pad wet past the timeout.

If you've given a sensor a job it wasn't sold for, I'd like to hear about it.

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Will Curran

I spent sixteen years building one company, and I have been in the event industry since 2007. These days I write about the technology I actually use — trucks, radios, home infrastructure, and the tools that survive past the first invoice.

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