This is an automated archive made by the Lemmit Bot.
The original was posted on /r/homeassistant by /u/rapax on 2026-03-21 14:19:28+00:00.
We have a nice little pond in our backyard, with newts and toads and all kinds of local wildlife. In summer, it's the jewel of our back yard. Unfortunately, evaporation often leads to low water levels, so we have to occasionally top it up.
I have a nice setup with a zigbee water valve that I can open and close through HA, no problem. What I don't have is a reliable water level sensor. That is obviously something that needs fixing, so I got to thinking about ways of measuring the water level (boundary condition: the sensor must not be visible to comply with WAF criteria).
- Floaters don't work, too many plants and algae etc.
- Ultrasonic needs a minimum distance of 10-20cm and while there is little wooden bridge over the pond, it's only about 10cm from the water, so not enough room to mount a sensor
So I came up with the idea of hiding a little wifi camera under the bridge and mounting a broken piece of a yard stick in front of it. Then use AI vision to read the water level. Worked beautifully at first: a little automation to wake up the camera every three hours, turn on the LED floodlight, snap a picture, pass it to Gemini, get back the water level, turn on the water if it's too low. Beautiful.
That is, until our helpful little spiders decided that what that setup really needed was a bunch of cobwebs right in front of the lens, so that they could reflect the light everywhere and make reading the water level impossible.
Ok, it's their home, I'll find another way.
Let's revisit that idea with the ultrasound sensor. Yes, there's no enough room to mount it vertically under the bridge, but what about horizontally? I added a 45° reflector panel under the middle of the panel, and placed a Shelly BLU distance sensor on a flat rock under the end of the bridge. I intentionally didn't mount the sensor to the bridge, because I wanted to be able to just reach under there and grab it, whenever the battery needs charging. Brilliant. Works perfectly well...for a few days.
It's now early spring, and the frogs are having a party. There's more frogspawn in the pond every morning and at night, they're loudly enjoying themselves. Cool. Suddenly, the vibration sensor of the Shelly triggers, then again, and the distance becomes implausible. Then signal is lost.
Turns out, that the Shelly is IP64 rated, but that doesn't mean it likes being kicked into the pond by horny frogs. So now the sensor is dead. 2:0 for the critters.
I have now ordered one of these zigbee sensors. Apparently they have a shorter minimal distance, and are mains powered, so no battery needed. I wonder what which little beastie will foil my plans this time.