Well water pressure switches work by detecting the air pressure inside the well's water-holding tank and using this to turn the water pump on and off. When the air pressure in the switch's tube can no longer hold the switch open, it engages the pump.
Water pressure switch settings may vary depending on the holding tank type, pump manufacturer or water distribution needs. Having a pressure switch set to low could cause the water pump to run excessively and potentially burn the motor out. If the switch is set too high, excessive pressure in the system puts unnecessary stress on the tank and pipes. Most systems have a water pressure gauge fitted to check against the switch settings.
The pressure-setting difference for when the pump cuts on and when it cuts off are relational and typically set with a 20-pound per square inch difference. Turn an outside spigot on and allow it to run until the water pump turns on, taking note of the pressure on the gauge. Turn the spigot off and let the tank fill, noting the pressure on the gauge where it turns off. Compare the two readings with the settings on the switch to determine if the switch is functioning properly.