My tank was installed in 1992. We have a lot of iron in the water so I made the assumption the tank probably needs to be replaced. Its working okay and holding the correct air pressure. But I'm replacing the old galvanized piping with brass and thought it might be a good time to replace the tank
It's up to you. I would not change the tank. I am not a pro.
Precharged Pressure tank flush:
1. Connect a hose to the sediment drain valve, and run that to where you plan to drain the water. I suggest filtering the output through a cloth or cloth sack if you suspect the sediment may include sand. That is just for curiosity.
2. Turn off the pump.
3. Open the drain valve, and let it drain until the water stops. It would be possibly interesting to watch the first and last water that comes out.
4. Close the valve, and turn the pump back on, and let pressure build.
5. Repeat steps 2, 3 and 4 a time or two.
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Also set the air precharge. The air precharge is always checked and set with the water pressure zero.