Why won't the valve turn off - Toro

1. Disconnect one of the valve wires.  Does the valve shut off?

• Yes,  the valve shuts off, the problem is with the timer. (Please refer to the manual of your controller) 
• No, the valve does not shut off. Check the bleed screw to make sure it is not loose or broken.

• Yes, low flow may prevent the valve from closing, compare the GPM (gallons per minute)/LPM (liters per minute) requirements of zone to valve specifications. 
• If the GPM/LPM is not within the specifications, add more heads to increase water flow or select a valve that works well at low flow rates.

• No, turn off the main water supply
• Remove valve cover and diaphragm. 
• Turn water back on and flush out for 15 seconds. 
• Inspect diaphragm for holes/tears replace if necessary.