I got a real surprise with my Iwata compressor yesterday. I decided to have two airbrushs (one SA, one DA) online all the time. So I had to add a T fitting to the output. Now, the compressor came with an adapter to convert some odd thread to the standard 1/4 pipe thread. When I hooked up the original brush I did wrap the 1/4 inch thread with teflon tape before putting on the airbrush hose and its 1/4 to hose fitting adapter. I did not, at the time, remove that weird adapter and apply teflon- I assumed it would be a pretty tight fit from the factory.
I liked the quietness of the compressor but was a little put off by the fact that I could get no more than 15 psi when spraying. At times, especially for flats, I like to go up to 20 psi. But, I got along with it okay for about nine months.
Yesterday when I was putting on that T-fitting and nipples, and doing a lot of tape wrapping, I decided to remove that original adapter and wrap the thread on the compressor output. When I got all the fittings complete and both airbrush hoses connected, I tried out both brushes. I suddenly had 30 psi with the air flowing! Apparently I had leakage at that original output, but not enough to hear it. But it was apparently enough to lower the pressure! Now, I have two brushes online, a silent compressor (well, nearly so) and can get both brushes as high as 30 psi. I probably will never use them that high, but at least I can get the 20 psi when I want it! So wrap ALL the fittings!