I am having trouble with my sprinklers not having enough pressure to make the sprinklers pop up and shoot out far enough. It's a 3/4" in-line system with four zones. We have changed the diaphragm and silenoid and flushed out each line. We don't see any problem with a leak and we have pretty strong pressure to our house. When we open the manual bleed the sprinkers work great but then you have to manually shut them off. We have adjusted the pressure valve on top of the valve and no change. The system has worked okay until recently and now there is just no pressure to make the sprinkers water correctly. Any suggestions?