Info, impact, causes, and troubleshooting a "Mainline High Flow Variance Shutdown" message.

Common Causes

• Broken mainline pipe.
• Zone valve stuck open which creates a high flow condition. 
• Flow variance limit is set too low.

What happens now? From the alert message:

• The master valve closes, Mainline 1 has no pressurized water and no water will be supplied to the zones until the variance message is cleared. Shown in 1.2 the site master valve is closed and Mainline 1 is isolated and all downstream zones are left without water.
• Expected vs Actual Flow (measured in Gallons per minute (GPM)). The controller expected 30 GPM from zones 13, 19 and 23 combined, but only measured 37.1 GPM. The controller attempted to shut down those zones, but the issue wasn’t resolved. This means the problem is related to the mainline pipe or another zone on the same mainline.
• Flow Variance Threshold (measured in %) is set to allow 20% variance, but the controller detected a 33.1%. There is a flow issue in one of Mainline 1’s zones; zone 13, 19 and 23.  

Troubleshooting 

• Find and repair any broken mainline or stuck open zone valve. 
• Adjust flow variance limit if it’s too low.
• Check for unexpected flow on, such as quick couplers, manually bled valves or any other flow the controller is not aware of. 
• Once issues have been resolved, clear the message to resume irrigation again. 
  • Go into BaseManager → find the flow variance limit → Flow Setup → Mainlines → In Flow Managementa 20% variance is set by default.
    • If the Shutdown box is checked, the system will trigger a message and automatic shutdown when the variance limit is exceeded. 
    • However, Advanced Flow Variance may be a better option, as it allows you to set different variance percentage based on expected flow ranges.
      • Ex: When the controller expects a combined flow of 25 GPM from zones, you might set 30% variance. But when the expected combined flow is 300 GPM, you can tighten the variance to 5% for greater precision.