Does air leak out of this area after it shuts off, or while it's running? Or both?

If it's leaking out of the small weep hole in the unloader valve, which is where the small tube connects to the pressure switch, then either this Unloader Valve is defective, or your tank Check Valve is.

Usually if air leaks out of the Unloader Valve on the Pressure Switch AFTER the unit shuts off, then it's indicative of a bad check valve. This happens because the in-tank Check Valve is stuck open somehow, allowing the pressure in the tank to back-feed through the lines; typically the leak occurs from the small weep hole in the Unloader Valve, which is on the bottom of the Pressure Switch, and which your smaller plastic line connects to.

- MTR

If the leak is originating from the pressure switch area I would say yes, replacing the pressure switch [should] do the trick. I can't be 100% sure of this, of course, since I don't have the unit with me to physically diagnose, but this is what sounds like the problem is.

I would certainly try to replace the plastic tubes first to see if that does the trick, if not then I would replace the Pressure Switch.

Good luck!

- MTR

Thanks for the comment!

I'm not sure if the original poster repaired the problem or not being he didn't reply, that I can tell. I would say that the pressure switch was most likely the problem. The only reason the check valve would need to be replaces is if the unit leaks around the pressure switch AFTER the unit shuts off (only).

If it leaks around the pressure switch while running only, then the switch needs to be replaced.

- MTR