Lorentz Lower Water Sensor Probe The Lorentz Low Water Probe contains a mechanical float with a magnet that actuates a switch. If the water level drops below the probe, the controller will stop the pump and the "Low-Water OFF" light will indicate. When the water level recovers, the controller will restart the pump after 20 minutes, giving time for the water level to recover. It is also possible to force a restart by turning the controller off, then on again.