The PGP rotors are built to withstand operating pressure of up to 100 PSI without blowing apart, but there can be other external factors that create problems. For instance, if there are slopes or even slight elevation changes, then the lateral pipes drain out. So when the zone first starts thereís an excessive amount of water flowing through the empty pipes at a high velocity. When that water stops, sometimes it can blow off nozzle turrets or break body caps. To help prevent the low head drainage and start up damage, install drain check valves in the PGPs which hold back about 3-4í of elevation change, or better yet, install the I-20 that comes with a stronger spring and check valve that holds back 10í of elevation change.
As for the nozzles themselves, they are designed to operate most efficiently at 40-50 PSI. If the pressure is higher, the water droplets are smaller and more misting and drifting will occur. And, if the nozzles are diffused to reduce the radius, that too may cause additional misting. How do you accurately check the dynamic pressure? Use a pitot tube shown below. Simply place the very small tube directly into the center hole of the nozzle and read the gauge. More importantly how do you reduce the pressure if itís too high? One possible way is to turn down the flow control on the valve, then recheck the pressure.
The leaking may be from caused from an old, deteriorated, hardened riser seal. That seal not only seals on the outside of riser that pops up, but it also seals against the inside of the body. Once the seal is old, it can shrink in size and harden, then it no longer is flexible enough to seal on the body, so water leaks below the cap. To return the sprinkler to nearly new condition, simply replace the riser seal and reinstall the head. For more information see the information below.