Precharged pressure (bladder) tank
A key component of many well pump systems
The primary purpose of a precharged pressure tank in a well pump system is to protect the well pump from excessive cycling which is the cause of premature pump failure.
How it works
What is a precharged tank? Try to envision a steel tank with a trapped, air-filled balloon. As water is pushed into the tank by the well pump, the "balloon" is compressed. When the pump switches off at it's high pressure limit, the pressurized air is pushing against the water. When water is used, the "balloon" expands and pushes the water out of the tank. In the diagram below, the diaphragm serves as the balloon. By prepressurizing a tank, we are able to get more gallons from each pressure cycle in your pump systems than in a plain tank. Good precharged tanks need minimal inspection and upkeep though they should not be neglected entirely since they can lose air slowly.
When your tank needs help
Here are a few indicators that your well tank may need attention: