Question
I have a sprinkler system, where the water pressure had fallen off, kinda weak, doesnt force some of the heads to pop all the way out. I had previously added some extra heads that didnt seem to affect the pressure. I checked the suction side pond screen, its all clear, I dont see any water leaks or air leaks in pump or fittings. Was thinking maybe one of the pump seals might be sucking air, the main exterior seal seems fine but really cant tell unless I take it apart and rebuild. Will see if the check value is sucking air, last time I checked didnt see that it was. Sprinkler heads seems fine, no excess water to indicate a leak. The main pipe in the pond was broken, I repaired it. But it seems there is a little dirt clogging some of my smaller heads, the pipe was fixed and the screen is fine. Could there be sand and stuff in the pump causing loss of pressure and dirt in sprinkler head screens. Also the 2 zone system not switching over a few times, took it apart and one time found a small shell blocking the mechanizm, but now it seems to work fine. Your ideas would be appreciated

Answer
The pump seal might be bad as you said. Also inside the pump is the impeller. That may be clogged. I've seen them clogged and reduce water pressure. Just the tiniest leak in the suction line will cause a lot of pressure loss. Since you have been finding things in the lines then it could be possible that the impeller is blocked.