Leaking Main Sprinkler Valve (Stop-and-Waste) Repair

A main sprinkler valve 4 feet underground leaks for 30+ minutes when opened, but sprinklers have good pressure. The valve uses a key and turns only a half-turn.

Diagnosis

This is a stop-and-waste valve. When closed, a side port drains the system. When opened, that port should seal. The leak indicates the sealing seat is worn.

Fix

1. Ensure the valve is fully open (counter-clockwise until a definite stop).
2. Work the valve back and forth to help the seat seal.
3. If it still leaks, the valve may need replacement.

Partial opening is a common cause of continuous drainage.