I recently increase the energize/de-energize setpoint on my submersible pump (my house has a well), from 20-40 PSIG to 30-50 PSIG. I then increased the expansion tank's charge to 28 PSIG. However, now every time I open the cold water faucet (any cold water faucet), some air spits out. I have a filter installed after the expansion tank and I can see air in the filter. The system quickly purges out the air and normal flow is re-established. I suspect that the expansion tank has some air trapped below the bladder. And, I assume that my well is not drying up. Question: How do I purge any trapped air in my expansion tank? Or, am I having different problem?

If the bladder tank has air under the bladder the pump put it there. I don't see how increasing the pressure would set up a situation where the pump would interject air into the system unless it was cavitating and sucking air. This could be caused by a lowered water table or it could be pulling air in through a small break in the suction line. Either way the problem lies on the suction side of the pump. Good luck, Tom

My pressure tank has a T fitting below the tank. All the water enters or exits the tank through the one opening in the bottom. If that is the case with you, then I don't see how air from the tank could enter the line since the air would tend to stay in the tank "above" the water. Of course, if the tank filled with air, then I suppose it would enter the line. But surely a tank with only air would cause your pump to short-cycle. At any rate, why not unhook the pump from the tank and just run the pump for a few minutes. I would think you would be able to see any air coming up from the pump. You might also want to go back to 20/40 and see if the problem follows the higher setting, although I can't see why it would.

Probably a shot in the dark, but simple to do so maybe it would be worth trying.

Seems strange that it only comes out the cold faucets.

Yeah... I suspect cavitation. I well water has a high iron content. The submersible pump becomes magnetized when running, which, in turn causes undisolved iron the water to adhere to the housing. Presently, I only get about 7-8 years on a pump because the pump's inlet becomes completely encrusted (clogged) with iron adhesions. A severely restricted inlet would certain result in cavitation. I guess I'll just have to pull the pump and inspect it. Thanks for your input.