Question
The zone one with my Toro system does not shut off.  It is the first to come on in the series as scheduled although it does not shut off on its own.  I turn it off at the screw on the manifold and it goes off. Once off, I turn it back on and it remains off until the next scheduled event.  What could be causing this unit not to turn off when scheduled?  LD

Answer
Try adjusting the valve.  First open the flow control knob all the way, then close it all the way, counting the turns.  Then open it back up halfway.  If this does not work, you may need to take the valve apart and clean it out, and inspect the diaphragm and other components.  If anything is torn or worn, replace it.