I assume the other 4 stations are working ok. You didnt say how much flow/pressure you have or what kind of heads are on the 6th station. 12 heads sounds like a lot of heads for a single zone. It seems that the flow and pressure you need exceed the available flow and pressure. The easiest fix could be to simply change the spray nozzles to lower flow nozzles if possible. If not, then I would consider dividing that station into two 6 head stations. Im guessing you have a 6 station controller, so no change there. Splitting it into two stations should be easier than trying to add a pump for a single station. Hope this helps...
