I've got an issue at a customers house that has me scratching my head. There are 2 zones in a island with grass the 1 zone no problems the other is like a pressure issue all the heads are MP Rotators. I took the valve apart nothing in it and the screen was clean. All the heads just bubble on this zone then slowly come up or not at all. I don't know if there is a pipe that's leaking a little but enough for pressure to drop. The home owner said she had seen this zone up one day and the next time it was just bubbling with some heads up about one inch. Thanks for any help or ideas and have a great week everyone.