I haven't been to this site this year, it's one that my #1 tech goes to. So hopefully I can convey the message right. We have worked on it for many years now. Older part of town, system is on very high pressure - 140 psi, 1" supply line. We are having problems with one zone. This particular zone is the only zone with rotors, all others are spray heads. I believe it has 10 RB 5004s on the zone. When the zone turns on, there is a quick surge, and the turrets get up, but then they won't go any higher. Usually, I would say this is from bad wiper seals, or too many heads on the zone and the zone would be stretched. BUT - if he forces the heads up, the zone is absolutely crankin'. Full resistance on the heads when he tries to push them down. Here are the things he has tried. He has nozzled it down to 10 GPM, and nozzled up to 20 GPM. Still the same thing either way. If he closes the ball valve at the PVB, turns on the zone, and slowly opens the ball valve, the zone comes up fine. But it won't come up with the quick turn on of a zone valve. He replaced the top of the DV with a flow control to see if he could get it to work with this slow opening situation. Still no after throttling down the valve. Do you think it could somehow be the high pressure? What if he put in a regulator for that zone (or at the PVB)? I will have him check pressure with his pitot tube and gauge this week. My other thought, is that since it is in an older part of town with big trees, maybe a root is starting to restrict it, and combined with the blow-by of the wiper seals at the initial turn on, there isn't enough flow to push the heads up. But that doesn't make sense when they come up by slowly turning open the BV. Any other thoughts?