Question about an air dryer Harbor freight

67Dart273, thank you. I now have a good understanding about that valve. I should read more thoroughly as I had already printed that out but did a lousy job of reading it! I guess I should take that drain apart and clean it because the unit sat for at least 2 years after he stopped using it and when I did the manually drain I got all that rusty condensation. i guess I should also put a bottle over the hose as well so it can drain itself without making a mess. Again thanks for you help.
Rod