Mechanical float switch for run-dry protection of PS2-100 solar pumps. The PS2-100 Well Probe provides a reliable method of run-dry protection. It detects that water is present within a well, tank or another water source. The Well Probe is typically attached to the riser pipe above the pump and connected to the controller. When the Well Probe becomes dry (water level is below the probe) the pump switches off to avoid dry running.