How do you fix a water logged pump.No drain plug.

Sounds like a water logged old style (galvanized) pressure tank, or a bladder type tank with either an incorrect amount of air pressure or a ruptured bladder. Typically the air pressure in a bladder type tank is set 2 to 4 psi lower than the cut in setting of the pump control switch. Check it using a tire pressure gauge with the pump off and the water drained using the lowest outlet in the system. if you don't have a drain plug (or better yet drain valve), now is the time to add one.