Clamp the bracket onto a sight glass or non-metal pipe and use any 18mm capacitive proximity sensor (link here
) to detect the liquid. It will detect through the sight glass! Use one to detect the high point and one for the low point (see example) and you can control the level between those points using a latching relay. The sight glass can be any diameter up to 1". Liquid level control just doesn't get any easier than this!
For water based fluids use an unshielded sensor. For non-conductive liquids, or small tube diameters, use a shielded sensor.