We have a La Marzocco Linea at the church and we draw a shot in about 12 seconds. Isnt this way to fast? We use the same brad grinder that self taps, to me, a non coffee drinker it is a little bitter.
It's too fast. Try to grind finer and go to 20 seconds and see if it is better, then grinder finer still and go to 25 seconds and compare, and go to 27 seconds and compare. Do you have grinder's make and model? Also, what brew temperature and pressure do you set your La Marzocco to?