I have one of six zones in my sprinkler system that the head no longer spring all the way up when that zone activates. We have had the sprinkler system in for 2-3 years and this problem just started. When that zone activates all the sprinkler heads in that zone pop up about 1 to 1 1/2" and and shoot water out, but they should be raising 3-4 inches. The don't raise high enough to spray out on the grass.

We have checked all the filters and cleaned them. We have capped off two of the heads to see if it that would verify it is a pressue issue, but they did the same thing. We have opened the valve and checked the diaphragm and checked it for a clog in the valve, neither were a problem. We have had two contractors out that deal with sprinkler repairs and they have not seen anything like this and don't know what to do.

Any help is appreciated.