[mike the moto]

So I answered my own question. It is my opinion that quick connect type air fittings should not be used for this application, unless you have lots of CO2 and don't mind a very very small leakage.

Replaced the quick connect couplings with 3/8" barbed fittings and hooked both hoses direct to the filter. No more leaks. Pressure is remaining in system with main gas valve on tank turned off. Just makes it a pain to change the filter.

Mike