Low Sprinkler Pressure After Line Flushing: Debris at Heads

An Arizona homeowner flushed rocks from a 4-zone ¾" system but pressure remained low—heads wouldn't pop up. Manual bleed worked perfectly; adjusting the valve's flow control, replacing diaphragm and solenoid didn't help. Water shot from the bleed screw when opened.

Rocks flushed from mains likely lodged at the head connections where pipe reduces to ½" or ¾". Check and clean each head's inlet screen. Also verify the main shutoff valve (often a gate valve) is fully open—partially closed or broken gate valves restrict flow. Listen for hissing at the valve body during operation, indicating internal restriction. The problem is likely debris at the heads or a partially closed supply valve, not the zone valves themselves.