Presure Tank

What are indications that a well pressure tank is going bad? I have good pressure but the pump cycles much more often that it used to. The pump stops at 40psi and starts at 20. The tank is 22 years old.

 

You didn't say whether you have a bladder type tank, or a galvanized steel tank.
If it's galvanized, and doesn't have any visible leaks, it still good. It's probably waterlogged. Turn off the power to the pump, open a nearby spigot and allow the tank to drain. You'll need to remove a fitting that will allow air to enter the tank. Once you do this, the air pad will be re-established and the tank will work properly.
If it's a bladder tank, depress the air valve on top of the tank (while under pressure). If water comes out, the tank is bad. If no water comes out, then turn the pump off, and completely drain the tank. Then check the air pressure in the tank with a regular tire gauge. There should be 18 psi in the tank for your 20/40 system. If not, add or remove air as necessary. If the tank will not hold air, it needs to be replaced.
Ron