Question about opening the drain valve to the wet tank to check for water/oil... I open the valve and high pressure air hisses out. I leave it open for 5 seconds or so, get nothing but air. Am I doing this right? Am I supposed to drain all the air out and see what comes out at the end? I know with my portable air compressors water comes out only at the end.
Absolutely correct. If your air dryer is working properly, you should never get water.
Yes, you are doing it right. If you follow the air line from the drain valve back to the air tank, you will see that the line comes off the
bottom of the tank. If there is any moisture in the tank, it will settle to the bottom and fill up the air line going to the drain valve. If you get dry air when you first open the valve, your dryer is in good shape.