I'm on a well & septic system that has been serving us well since its
installtion. I'm curious about a recent anomoly that has me concerned that
something may be about to quit.

The problem was (is?) air in the pipes. In every faucet, including toilet
tanks, we experienced a few days where we'd occasionally get that familiar
explosion of air & water when we'd turn on the faucet. In recent days, the
problem appears to have diminished (SWMBO hasn't complained about it.)
What may have caused that? There was no water discoloration, and the water
pressure seems fine otherwise and has been fine since. FWIW, the
submersible pump is about 8-10 years old and the pressure tank is closer to
17.

As a descriptor of the effect, it was similar to what happens when the water
has been turned off for a while for a repair, then turned back on. That
little spray as air clears the pipe is what we experienced.

It's almost as though the well may have gotten low & the pump sent air into
the system, but it's certainly not been drought conditions here
(mid-Atlantic), and we've always seemed to be on a good aquifer, even in
very dry spells. Is there anything about an aging pressure tank that could
result in this sort of symptom?