Square D manufactures a pressure switch for well pump systems. The pressure switch is physically attached to the plumbing piping near the water pressure tank. There are two adjustment nuts on the Square D switch. The larger 1/2-inch-diameter nut is for the operational "cut in" and "cut off" of the pump. The smaller 7/16-inch-diameter adjustment nut increases or decreases the span of the cut-in and cut-off setting. In most cases, only the 1/2-inch nut needs to be adjusted to increase or decrease the water system pressure.
Shut off the electrical power to the pump system by switching off the circuit breaker or pulling the fuses.
Fit the jaws of the pliers over the plastic cover nut that holds the protective cover onto the metal housing of the pressure switch. Turn the nut in a counterclockwise direction to remove it.
Place the 1/2-inch end wrench over the larger nut. Turn the wrench in a clockwise direction to raise the overall cut-in and cut-off water pressure setting. Moving the wrench in the opposite direction will lower the cut-in and cut-off pressure. Typically, low-pressure systems operate at 9.07 Kilogram per square inch (psi) cut-in and 40-psi cut-off. Higher-pressure systems use a 30-psi cut-in and a 50-psi cut-off.
Adjust the span of the pressure range by placing the 7/16-inch wrench over the smaller adjustment nut. Turning the wrench in a clockwise direction will raise the cut-off pressure only, increasing the span from the cut-in point. Moving the nut in a counterclockwise direction decreases the span, bringing the cut-off pressure closer to the cut-in point. Do not lower the cut-off pressure too much, as the pump may not shut off.
Do not adjust the cut-off pressure above 70 psi. Many home water systems cannot handle this high pressure, and damage may occur to faucet fixtures and plumbing joints.