Two Switches to Control a Pump
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Pump control circuit.

How it works:


As the tank empties the TOP switch closes first.
When it passes the low-level switch it closes and RLY1 is energised.
The pump starts via contact RLY1b.
Meanwhile RLY1a bridges out MIDDLE so that the pump continues to run as the water level passes that switch.
RLY1 remains latched on until the top switch is opened.


Rate the relay coil for your control voltage. Rate the relay contacts for your pump voltage, AC or DC as required, and pump starting current.