To install a water well pressure tank, cut the electricity to the well's pump, drain the tank, release the pressure from the lines, remove the old tank and install the new model. The process requires some mechanical ability, a few tools and a helper.
Shut off the electricity at the main house breaker panel. Open the relief valve on the inlet line and allow the pressure to escape. Open the drain valve and let the water flow out of the tank.
Using a pipe wrench, loosen the nuts on the inlet and outlet lines and disconnect the lines, but leave the nuts on the threads. Clean the pipe threads of any rust with a wire brush. Remove the nuts on the anchor bolts holding the tank to the concrete pad with a socket wrench. Remove the old tank.
Wrap the inlet and outlet threads on the new tank with appropriate sealing plumber's tape and reconnect the lines, but don't tighten the nuts. Put the tank in position over the anchor bolts. Ensure the inlet and outlet points are aligned correctly so there is no tension on the pipes, then tighten the nuts. Put the nuts and lock washers on the anchor bolts and tighten them securely.
Leave the relief valve open and turn on the electrical power. Leave the valve open until the air escapes and water streams out. Close the valve and allow the tank to fill.