[villagetinker]

Originally Posted by Schmitth

I don’t think the sprinkler head is clogged. I took off all heads (and removed the filters) in that zone (9), and pressure for seven of sprinklers had a water output of say one foot, the other two sprinklers the water barely trickled out.

From what you have done and what you described, I see only 2 options, a leak, or a restriction. In either case you will probably need an irrigation specialist to see if they can find the problem without having to dig up a lot of piping. I bought a leak detecting microphone (off Amazon ~$40) but it only extends around 4 or 5 inches, which is not deep enough for irrigation lines which seem to be 12 to 18 inches deep. 'One other item you could try would be to temporally cap all of the working spray heads, then turn on that zone and loo for water, this would be the area of the leak. If flow to the other heads does not improve then I would assume a definite restriction between the last working head and the first non-working head.
Hope this helps.