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?