AIR PRESSURE REGULATOR

I have a problem with my airbrush set up and need some sage advice.

I have a 5 gallon air compress. that I run to my air brush thru a 20 ft. air line.  At the air brush end, I have a water trap & regulator.  When I turn the valve on the air tank to "on" I can't get a consistant flow rate (p.s.i).  It's either extremely high or almost non-existant.

Thanks

Source: http://cs.scaleautomag.com/SCACS/forums/thread/988656.aspx

Zsolt Baumgartner Elie Bayol Don Beauman