WorthFlorida
New chemo regiment started Aug 20th.
Both valves must be open for water to flow. You may have some valves stuck in the open position. Those diaphragms can get hard or debris is in them. Perhaps a neighbor or a lawn guy came buy and noticed your sprinklers going off so he turned the valves on the preventer to save the day. Last fall I had to turn off my neighbors water meter off (a reclaimed water system here in Avalon Park, FL for irrigation) because one zones would not shut down. I never could find the bad valve but she had someone fixed the system for her.
https://www.zurn.com/products/water-safety/backflow-prevention/950xlt2
https://www.zurn.com/products/water-safety/backflow-prevention/950xlt2
