Anyone dealt with that before? Could it be the tank itself? How the hell do i find it? Soap and water failed miserably, perhaps because the leak is very slow (I get down from 175psi to 120psi or so in 24 hours). Ideas would be very welcome.
This is NOT a small leak. With a pressure drop like that there have to be bubbles in a soapy water test. Try submersing the entire tank in a bucket of water. If it is the tank you will see bubbles.