Tom,
Assuming that your 2008 PT like our 2006 PT and has a gravity fill for the freshwater tank and a hose reel for city water. I don’t believe that there is a Swan Quick-Fill valve installed.
There is a check valve that prevents stored water from back feeding when the water pump is in use. I’ve included an image below. From my experience with our PT, when this check valve fails water will leak out of the hose reel connector.
If your coach has an auto-fill function via the Aladdin system, it is possible that the Red Hat electric valve is allowing air to enter the system.
Another place to look, if your coach has the Prevent-a-Freeze winterization system, the changeover valve could be allowing air to enter the system. On our coach, the Prevent-a-Freeze changeover valve is mounted on the forward bulkhead above the Aqua-Hot.
-Scott