Using a capacitor sensor to detect a water level is a simple method of sensing. This circuit uses C5, which
is 10" to 20" of #22 enamelled wire as one electrode. This shifts the oscillator, an NE556 timer, in frequency. The frequency shift depends on the capacitance change, which in turn varies with water level. A meter connected to pin 9 of the 556 is used as an indicator. C5 can be made larger or smaller to suit the intended application.