Choosing the Right Tank
Be sure you have the proper type of tank for your needs. There are two main types of pressure tanks: diaphragm and galvanized tanks. Diaphragm tanks don't require air charging valves in the pipe system since they come pre-charged with air, unlike standard galvanized tanks. If a diaphragm tank is replacing a galvanized tank, all existing air volume controls must be removed and snifter or bleeder valves should be plugged.
Removing the Old Tank
Ensure the well pump is turned off at the breaker. Cut the pipe from the pump as close to the old tank as possible, allowing the maximum amount of spare pipe for the installation of the new tank. Most tanks are piped with PVC, which is easy to cut with a handheld circular saw. If the tank is bolted down, undo the bolts with a steel wrench and remove them. It's now possible to lift and remove the old tank.
Glue a 12-inch-long piece of PVC pipe into a correctly sized PVC male adapter. Tighten the adapter into the tank elbow using at least four layers of teflon tape. The tape must be tight and secure to avoid any leaks. Hold the tank upside down or, if it's an extra large tank, on its side to get the best grip for tightening. When you're finished, turn the tank back over onto its base. The tank's air pressure must then be adjusted to conform with your pressure switch setting prior to installation. Most diaphragm tanks come with a factory pre-charge pressure between 28 and 38 pounds per square inch.
Use a plastic barbed fitting to connect the exposed pipe from the pump to the tank elbow. Reinforce the fitting with at least four layers of tightly wrapped teflon tape. If the barb is too tight to fit over the pipe, use a heat gun or hair dryer to loosen it first. Use a stainless steel hose clamp to secure the fitting extra tight. If necessary, bolt the tank back into the ground for added stability. Turn on the tank to test that it's working and doesn't leak.
Tips and Precautions
A pump that's cycling on and off repeatedly and rapidly when in use is indicative of a bad well pressure tank. One of the most common problems that tanks face is waterlogging, where a small hole or tear develops in the diaphragm. Water will flow through the hole and into the tank's upper chamber, -- which is intended for air -- eventually causing the tank to stop performing properly. It's important to replace a bad pressure tank as soon as possible, as rapid and repeated cycling will ultimately destroy the pump. And tanks are far less costly to replace than pumps.