Abstract: A variable differential adjustor for a fluid pressure-actuated switch, with the fluid, in the preferred form of the invention, being air. The restrictor has a restrictor housing with a fluid passage in which a restrictor plug, typically a set screw, is engaged. By judicious adjustment of the position of the set screw, fluid flow to and from a pressure-actuated switch is controlled, controlling when the switch is activated to control apparatus such as a sump pump, and when the switch is deactivated.

Abstract: A basement flood control system for use in a structure having a basement floor located below ground level and having a sump pit or other collection basin for gathering subterranean water. The system has two primary pump units operated with line current, a battery-operated back-up pump unit, and a sensor arrangement for sensing water level in the collection basin. A controller is connected to the sensor arrangement and the pump units for variously activating the pump units singly or in any combination responsive to the water level detected by the sensor arrangement.