Steve,

I have just a few questions. Are your pop-up housings below the grass or ground level of your lawn? Do you apply granular fertilizer, sand or other amendment to your lawn periodically? Have you checked the amount of play between housing and pop-up shaft. RB42SA & RB5004 are a pretty darn good products. Have you asked the experts of Rainbird about your problem? How clean is your water supply source? What is your systems pressure? How many heads per zone? Just curious? Aloha

The heads are at ground level. I do use fertilizer two or three times per year. The housing and shaft seem pretty tight when installed, and the water supply is potable water from the city system and is clean. The system static pressure is 38 - 40 psig at the tie-in point and and about 30 psig at the system end. There are twelve zones with 5 pop-up heads each and two zones with 6 sprayers each.

The individual units never have a problem with dirt or grit inside the housing. The strainers are always clean and the springs seem to be in good shape when replaced. The problem appears to be the seal between the pop-up shaft and the housing. The shafts develop deep groves where dirt and grit has lodged between the housing top and the shaft. There is always enough pressure to pop them up, but over time the build up prevents them from retracting. It there was a way to disassemble the shaft from the head and replace the shaft seal (if there is a shaft seal) I believe they could be cleaned and reused.

Rain bird used to make a different pop-up head that had a smaller diameter shaft and a larger housing. They also rotated much faster than the 42's. I installed several of those maybe four or five years ago and all of them still function like they should. I can't remember the model number, but it appears rain bird discontinued that particular head - at least I can't find them anywhere.

Steve,

After mulling over your data, I can't see anything that might cause the problem. The grit is getting in there somehow. My guess is the residential grade RB42sa is not up to the tasks, conditions and your lower pressure for the system you are operating. I would stick to the RB 5000 professional grade or another brand like Hunter. GL JMHO Aloha.