I have a "pompe a eau" inside a well of 40 meters length, the water pump doesn't stop if there is no more water in the well and that causes damage to it. So I tought of using water level sensors just above the hole from where the water pump drains the water, so that when there is no more water I can turn off the circuit so that the water pump stops working.
I have a little knowledge of electronics(but good programming skill, I can program arduino or some other microcontroller without any problem).
So I have looked for water level sensors in eBay and I found this.
The problem is that the cable lenght is just 400mm, its too short for doing anything with and is this item capable of taking pressure because the "pompe a eau" is going to be 10-20 meters under the water.
Maybe this is not the right sensor for the job?
Just buy a pump with integral float switch (that's the red thing): -
I use a similar one to this to pump waste water from my koi pond 10m up a slope to a drain. It works but, if you don't value your time enough to spend (maybe) $100 then my advice is useless.
Try searching "submersible water pump with integral float switch". Of course the 10m depth means you have to possibly refine the search parameters.