Spraygun Air Pressure Basics

How to match your compressor to your gun and set the proper pressure. February 17, 2014

I'm running a 60 gal 13.4 cfm air compressor with an off the shelf air dryer. To this I attached a 50 lf hose. I have an air pressure controller on the bottom of my cheapo cup gun. For some reason I notice the pressure drop after the trigger is pulled. Usually takes about 3-4 seconds for the air pressure to drop about 5-10psi, but I find myself compensating by adjusting the air regulator. Any idea why? I haven't been spraying for a long time. Long enough to want to get away from my finicky husky hvlp "pro" gravity cup gun!

Forum Responses
(Finishing Forum)
From contributor D:
That is just a restriction valve. It won't act like a pressure regulator. You are just providing a smaller hole for air to flow through. You have to get a regulator setup. Cheap one is about $50 and that will solve your problem.

From contributor B:
You did not say what size hose you are using. The air hose should be at least 3/8" dia. Also, the longer the hose the more the pressure drop. Check how much CFM the gun requires. If the gun requires more air than the compressor will deliver, the pressure will continue to go down and the compressor will never be able to keep up to the demand of the gun. That said, it is not unusual for any system to fall a few pounds once the gun is triggered. Set your pressure with the trigger pulled and you should be fine if you have the right size hose and the compressor is large enough to cover what the gun is demanding.

From Paul Snyder, forum technical advisor:
Always set the air pressure to the gun with the trigger pulled. It's normal for the pressure in the line to drop off as you allow the air to escape.