How Much Air Do I Put in My Well Pressure Tank?

Well Pump

• The well pump sits deep inside the well, close to its bottom or past the point the well level drops, when the well is more than 25 feet deep. It pulls in water through a series of veins and pushes it up the pipe. From there, water passes by an in-line pressure switch before entering the air bladder tank where it is stored for use. Well pumps are rated by horsepower, size and gallons-per-minute water delivery.

Pressure Switch

• In-line between the well pump and the pressure tank, you’ll find a pressure switch. The pressure switch sends the signal for the pump to kick on when the pressure drops in the air bladder pressure tank. Pressure switches usually come present to 20 lbs. per square inch -- or psi -- from the factory, which is a low setting for water delivery, especially if the well is below the level of the house. Most pressure switches require adjustment to a higher setting, which in turn requires the pressure inside the air bladder tank to be adjusted.

How the Tank Works

• Inside, at the top of the tank, an enclosed air bladder pushes against the water in the tank when demand from the home is placed on the water delivery system. The pressure switch is set to kick on the pump based upon the pressure inside the tank, when the tank empties and the point at which the switch has been set to kick on the pump. The tank has an air valve used to check the air pressure inside and for adding air, as needed for efficient water delivery.

Filling the Tank

• While the air bladder tank comes prefilled with air from the factory, like the pressure switch, it is often not at the right pressure needed for efficient operation. Use a tire gauge to test the air pressure in the tank and then add air as needed to match the setting on the pressure switch. If the pressure switch is set to kick the pump on once pressure drops to 30 psi, then the air in the tank needs to be at least 2 psi below the pump kick-on setting. If the pump kicks on at 30 psi, then set the tank to 28 psi. Add air to the tank through the valve used to check the air pressure.