Step-by-Step Guide

Understanding the Message

The Mainline High Flow Variance Detected message indicates that the controller measured a higher flow rate than expected from the zones running on a specific mainline. This is an alert-only message that notifies you of a potential problem but does not automatically shut down any zones.

The message includes several key pieces of information:

• Date and time of the event
• Priority level (typically low for this alert)
• Main line number affected
• Zone numbers that were running during the event
• Variance threshold versus actual (measured as a percentage)
• Expected versus actual flow (measured in gallons per minute)
• Zone shutdown status (whether zones were shut down)

In the example message, the controller expected a combined total of 82 GPM from zones 13, 17, and 39 running on mainline 1, but the actual flow measured was 104.2 GPM. The variance threshold was set to 20%, but the controller detected a 27.1% variance. Because the variance shutdown feature was not enabled, the controller could not shut down any zones and only generated an alert.

Only the zones on the affected mainline are impacted. In this example, zones 13, 17, and 39 are on mainline 1, while mainline 2 is not affected.

Common Causes of High Flow Variance

Several conditions can trigger a mainline high flow variance alert:

Broken mainline: A break in the mainline itself will cause water to flow freely, resulting in higher-than-expected flow rates.

Stuck zone valve: A zone valve on the affected mainline that is stuck in the open position will create a high flow situation by allowing water to flow through an additional zone that should be closed.

Flow variance limit set too low: If the variance threshold is configured too tightly, normal fluctuations in flow may trigger false alerts.

Flow variance shutdown feature disabled: When this feature is disabled, the controller can only alert you to the problem but cannot take corrective action by shutting down zones.

Troubleshooting High Flow Variance

1. Check the mainline for breaks. Inspect the mainline associated with the alert for any visible breaks, leaks, or damage that could cause excessive water flow.

2. Examine the zones that were running during the high flow event. In the example, zones 13, 17, and 39 were the suspects. Inspect each of these zones for problems that could cause high flow:

• Stuck zone valve that remains open
• Broken lateral lines
• Broken sprinkler heads

Adjusting the Flow Variance Limit

1. Navigate to the Flow Setup tab and select Main Lines under Flow Management.

2. Review the current flow variance limit. A 20% variance is a good starting point for most applications.

3. Consider whether the current variance threshold is appropriate for your site conditions. If you're receiving frequent false alerts, you may need to increase the percentage. If you're missing actual problems, you may need to decrease it.

Using Advanced Flow Variance

Advanced flow variance allows you to set different variance percentages for various expected flow ranges, providing more precise control over when alerts are triggered.

1. Access the advanced flow variance settings in the Flow Setup tab under Main Lines.

2. Configure different variance percentages based on expected flow ranges.

 For example:

• When the controller expects 25 GPM of combined zones, set a 30% variance to account for greater variability at lower flow rates
• When the controller expects a combined total of 300 GPM from zones, set a tighter variance of just 5% since higher flow rates are more stable and predictable

This approach allows you to be more lenient with variance at low flows where measurement accuracy may be less precise, while maintaining tighter control at high flows where deviations are more significant.

Enabling High Flow Variance Shutdown

1. Consider enabling the controller to shut down on high flow variance. This setting allows the controller to both generate a message and perform a shutdown if the variance limit is exceeded.

2. When shutdown is enabled, the controller gains the ability to isolate and shut down the specific high flow zone, which helps narrow your troubleshooting search and prevents water waste while you investigate the problem.

Video Walkthrough

Video originally published June 2021.

If you have questions, here are 3 ways to get answers:

1. Search within this HydroPoint knowledgebase

2. Visit the HydroPoint support page

3. Call 800-362-8774 or email support@hydropoint.com, hours are Mon-Fri 3:00 AM – 6:00 PM PT and Sat 9:00 AM – 2:00 PM PT.