Simple fluid flow indicator

There have been a number of LoRa use cases in this Forum that rely on fairly accurate water/fluid flow meter measurement sensors. In effect, they use LoRa to simply transmit meter readings.

However there are Use Cases which only require data if water/fluid is moving within a pipe (not the fluid flowrate and volume etc).

This very basic data (fluid moving/not moving) may provide useful information:
for example:- unexpected flow of water within a house water pipe may indicate that the pipework has broken elsewhere, or that someone is in a property and using water. There are clear agricultural use cases in irrigation also.

As always, cost and reliability of the sensor itself is key.
So, before I rush out and start buying a bunch of sensors…I thought I should ask the TTN community.

Has anyone had experience of using non-intrusive simple sensors that reliably indicate that fluid is flowing in a pipe?
Also, has anyone attempted acoustic or vibration sensors to achieve this?

these types are the cheapest you’ll find

but they are ‘intrusive’, you have to mount them in your system.
non intrusive types don’t work (cheap) for metal pipes

thanks @BoRRoZ, but these are intrusive. You need to break the pipe to install them.

I have seen some of the new ultrasonic ‘clamps’ that fit onto the outside of the pipe, but they are very expensive and are designed to monitor flowrates quite accurately.

these ‘clamps’ probably only work on non metal pipes

Sorry, I forgot to mention the recent thread on level sensors in this forum. That was the discussion that got me thinking about this…!

I am not sure this type of sensor would pick up whether fluid was moving or not. However I will track down the datasheet and check, thanks