Locate the dedicated circuit breaker for your well pump in your home's main electrical panel. The breaker is typically labeled 'Well Pump', 'Pump', or something similar. Flip the breaker to the 'OFF' position. To be absolutely certain, test a faucet; if the power is off, the water will run until the pressure is gone and will not restart. For an added layer of safety, use a non-contact voltage tester on the wires at the pressure switch to confirm there is no live current.

Open a faucet at the lowest level of your house, such as in the basement or an outdoor spigot. This will allow gravity to help drain the water from the plumbing system and the pressure tank. Let the water run until it slows to a trickle. Place a bucket under the tank's drain valve (if it has one) or the main connection point to catch residual water.

First, carefully disconnect the electrical wires from the pressure switch. Use a screwdriver to loosen the terminal screws and pull the wires free. Next, use two pipe wrenches or a pipe wrench and channel-lock pliers to disconnect the main water line from the tank tee. Use one wrench on the fitting and the other on the tank tee itself, applying opposing force to prevent twisting the pipes. For PVC, you may need to cut the pipe with a hacksaw or PVC cutter if it is cemented in place.

With all connections severed, carefully tilt the old pressure tank to drain any remaining water into your bucket. These tanks are awkward and can be very heavy. If it's a larger tank, use a hand truck or dolly to move it out of the work area. Place rags on the floor to absorb any spills.

Before installing the new tank, you must set its internal air pressure. Locate the air valve on top of the tank, which looks like a tire valve stem. Use a tire pressure gauge to check the factory pre-charge. It must be set to 2 PSI *below* your pump's cut-in pressure. For a 30/50 PSI switch, the cut-in is 30 PSI, so you must set the tank's pre-charge to 28 PSI. Use an air compressor or bicycle pump to add air, or press the pin in the valve to release air until you reach the correct pressure. The tank must be empty of water when you perform this check.

Prepare the threads of your new tank tee, pressure gauge, and any other threaded fittings. Wrap the male threads with 3-4 layers of Teflon tape in a clockwise direction (the same direction you will tighten the fitting). After wrapping with tape, apply a thin layer of pipe dope over the tape. Screw the new tank tee into the threaded connection at the bottom of the pressure tank and tighten it securely with a pipe wrench. Then, install the pressure switch, pressure gauge, and pressure relief valve onto the appropriate ports of the tank tee, tightening each one.

Carefully move the new, fully assembled pressure tank into its final position. Align the tank tee with the main water line coming from the pump. Reconnect the plumbing. If using threaded connections, apply Teflon tape and pipe dope. If using PVC, clean the pipe end and the fitting with PVC primer, then apply a liberal amount of PVC cement and push the two pieces together with a quarter-turn, holding for 30 seconds. Ensure the tank is stable and level on its base.

Open the cover of the pressure switch. Referencing the photos you took earlier, reconnect the electrical wires to the correct terminals. Typically, there are two terminals for the power from the breaker and two for the wires going to the pump. Ensure the copper wire is securely under the screw heads and tighten them firmly. A loose connection can overheat and fail. Replace the pressure switch cover.

Ensure the faucet you opened earlier is still open. Close any other faucets. Go to the main shut-off valve near the tank and open it SLOWLY. This allows the system to fill gradually, preventing a violent 'water hammer' effect. Once water is flowing steadily from the open faucet, go to the electrical panel and turn the breaker for the well pump back to the 'ON' position. The pump should start. Immediately check all new pipe connections and fittings for any drips or leaks. Use a flashlight to get a clear view. If you see a leak, turn the power off, drain the system, and tighten or re-do the leaky connection.

With the pump running, watch the pressure gauge. The pressure should rise until it reaches the cut-out pressure (e.g., 50 PSI), at which point the pump should shut off. Now, close the faucet you had open. The system should hold pressure. Open a faucet elsewhere in the house and watch the gauge again. The pressure will drop, and when it hits the cut-in pressure (e.g., 30 PSI), the pump should turn back on. Let the pump run through a few cycles to confirm it is working correctly. Go around the house and open faucets one by one to purge any air trapped in the lines until they run smoothly.