To install a pressure switch on a water well tank, turn off the electrical power, remove the cover, disconnect the wires, remove the old pressure switch and put the new pressure switch on. The task requires no special skills and needs a minimum of supplies and tools, including a pair of pliers, a screwdriver, a pipe wrench, wire brush and plumbers tape or pipe sealant. A voltmeter and masking tape make the job safer and easier.
Throw the emergency disconnect or trip the main breaker for the well in the house electrical panel to cut off the electricity. Remove the acorn nut on the outside center of the pressure switch cover and lift off the cover. If you have a voltmeter, test the terminals on the pressure switch to make sure there is no electrical flow.
Loosen the terminal screws, and remove the four wires attached, making sure to note where each one goes. The leads are marked T1, T2, L1 and L2. Having masking tape to mark each wire makes it easier to remember where they go. Remove the locking nut holding the wire conduit to the switch. Move the conduit and the wires out of your way.
Rotate the pressure switch counterclockwise, and unscrew it from the mounting nipple. Clean the mounting nipple threads with a wire brush, and wrap them with plumbers tape or sealant. Hand tighten the new pressure switch into place.
Reconnect the conduit with the locking ring to the pressure switch body, and reattach the wires to the correct terminals. Replace the switch cover, restore electrical power, and inspect for leaks.