reply to alphapointe
Re: Compressed air dryer ready to make me scream. Most air dryers I've seen use either a float valve or an electronically timed solenoid valve to dump the accumulated water when required.
Perhaps the dump valve in your air dryer is not functioning correctly and is staying open causing the loss of pressure.
Any leak that you need soap to find, is not going to cause enough loss to cause any problems, unless the compressor is seriously underrated for the task. The leak is most likely quite significant, which is what leads me to believe it's the dump valve.