The stuffing box should leak. Leaking at 1 drop every 20 seconds is about right for "flax" packing. It should leak less when not running and leak it should. You can go to synthetic packing and drip far less especially when sitting. There is also a dripless available for a price.
The "gland" can be tightened a tiny bit at a time to reduce the drip, however your in the ball park right now.
Does the stuffing box feel warm when running? Should not be hot. You should be able to hold it without discomfort.
Dave Neptune