Question about an air dryer Harbor freight

Did you read the "user manual?" You can download it right from HF. These are basically a refrigeration unit (dehumidifier) Surely the drain system was meant to be automatic

The drain valve has a float valve inside, page 8

Compressed Air Dryer

Harbor Freight Tools – Quality Tools at Discount Prices Since 1977


/compressed-air-dryer-40211.html

You have to copy/ paste the two links together as the crap software from this site causes the pdf to "display" rather than be a simple link