I have anti-siphon type valves and have replaced the heads with automatic units. The automatic heads I am using are Champion and Orbit. They seem to work great when they are new, but tend to work poorly over time, until finally not allowing the sprinkler to come on at all. This happens over many months. I have found that if I remove the solenoid and drill out the hole in the valve seat just slightly, the valve starts to work properly again. If you drill out the hole too much, you ruin the valve ...
