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Comment by geomark | Hacker News Reader

Nice project. Mine isn't quite so ambitious (yet). I just need to monitor water pumps. Does anyone have a suggestion for a water flow sensor? I need to detect if there is water present at the pump input. So far the only thing I've been able to get my hands on is a water flow meter [1]. But it's overkill because I don't need to measure flow rate, only presence of water.

[1] https://www.aliexpress.com/item/Black-G1-Inch-Water-Flow-Hal...

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If you don't care about precision (and depending on what your pipes are made out of), you could make a DIY version of that sensor (that you could wrap around the pipe, rather than having to cut it to put it inline).

https://www.youtube.com/watch?v=TR0baWuB6v4

Could you use something to measure resistance? Like two wires, so when immersed resistance drops?

I'm sure that would work, at least initially. I'm concerned about reliability. My water has very high levels of calcium carbonate which quickly scales up everything. I think the electrodes wouldn't last long. A nonintrusive solution would be great. I've seen nonintrusive water flow sensors that use ultrasound to detect the flow of water. They are industrial devices and their price makes them unsuitable for my use.

There are cheaper optical water level sensors in the aquarium trade that might work for you. Check out the Tunze Osmolator as an example. It could easily be connected to a GPIO on the pi.

That's a very interesting idea. Thanks for the suggestion. It is still invasive since I have to cut the intake pipe and insert a section with the sensor installed in it. But it is more flexible since I can install it in any size pipe. And for my use case of a 1 inch input pipe it can be cheaper than my current solution. For example https://www.aliexpress.com/item/15mA-5V-Optical-Infrared-Wat...

Although, I wonder if scaling (as in hard water scale) is still going to be an issue.

https://youtu.be/wh0OoLUTeM8

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