Air is gettting into my hot water line.

Cold water can hold more air than warm water. That is why fish die when streams get warm and it is why you see air bubbles form when a pot of water is heated on the stove.

If you treat the water with aeration for iron, the water can have more air entrained than normal and that air may be driven off inside the water heater.
 
It could also be that air is getting in on the suction side and the house plumbing is such that a vertical Tee off for the HWT acts as an air separator.
 
Your pump has a leak on the suction line.
Maybe so, maybe not. Since it is a driven well, it could simply be that it is shallow enough that the cone of depression is letting in air at the top of the sand point.

The OP has not really quantified the air and whether it is constant or simply a small amount on first draw after a time of no use.

Both theories I put forth apply to me... small amounts of entrained air are driven out by the water heater and the vertical Tee off for the HWT is the first Tee in the line. When the AVC on my precipitation tank sticks and surplus air is forced through the iron filter and softener, it collects in the vertical line to the HWT. A stuck AVC was causing the media in my iron filter to carry to the drain and clog up the valves during backwash.

I had a neighbour replace his precipitation tank with a standard bladder tank and so had no AVC to remove the air. When air would get so bad as to knock a glass out of his hand, he would do a manual backwash of the iron filter to purge the air.
 
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