Hi, I want to build my own automatic watering system, with the reservoir being just an ordinary bucket. There's a number of options to detect water level, from the top off my head:

1. Ultrasound sensor
2. Weight/pressure sensor
3. Floating sensor
4. Contact-less sensor
5. Droplet sensors

et cetera.

What I want is just to detect when to refill the bucket, i.e. not much resolution is needed, I basically only need two states - "enough" and "empty". However, I'd rather have something that doesn't stick out too badly and can be easily hidden just so that the bucket is visible.

Can I maybe just stick two wires in the water, connect one to +5V and periodically read the other as GPIO? Would the conductivity of water be enough for this to work? Or maybe, are there other problems with this?

Thanks in advance!