What could cause air to get into your water lines in your well water system?

Air in water lines

It's possible that your jet pump could be sucking air from your holding tank. There is usually a float switch from your well to the holding tank depending on the system. The float switch determines how much water is pumped into the holding tank. if the holding tank isn't full enough your jet pump could create a vortex in the tank causing it to suck air. It could also be the case if your jet pump is oversized. It could be a serious problem depending on how much air is being sucked through the pump.
More input from FAQ Farmers:

• According to my electric water heater manual, if the system is idle for long periods or the heater is not working correctly, hydrogen gas can be produced and that "air'" in the system might not be air, but might be gas. I have no idea how to tell if it is one or the other.

• Our pump maintenance company just pulled and replaced our pump today to cure an air-in-the-line problem. The internal check valve on the outlet side of the submersible pump had failed (Gould pump, rather flimsy looking plastic check valve). Old check valve and spring was removed, new external brass check valve was installed. Hope this helps.

• ...or there is that dreaded, "Eeeek! Our well has gone dry." Despite pleas to conserve water, our useage just keeps going up and as a result of this, water tables do drop.

• If You have a bladder-style pressure tank the well could be running dry,or a hole in the drop pipe in the well or a failed check valve.With all the water off watch the pressure gauge,if the pressure drops then it is a hole or bad check valve. A captive air pressure tank has a air volume control valve that may be bad.

• It is more than likely the foot valve at the bottom of the well is not holding the pressure in the pipe from the well to the pump. They wear out over time and are cheap and simple to replace

• I have a problem w LOTS of air getting in our well water system, somewhere before the pressure tank (the pressure gauge holds steady, not losing pressure). How can it the solution be the check valve or the pitless adapter in the well if the pressure gauge is holding steady? Not sure where the air is coming from...any ideas?