Step-by-Step Guide

Understanding the Message

The Mainline Low Flow Variance Detected message indicates that the controller detected a flow rate lower than expected on a specific mainline. 

The message provides several key pieces of information:

• Date and time: When the variance was detected (e.g., January 1st, 2021 at 8:30 AM)
• Priority: Low
• Mainline: Which mainline is affected (e.g., Mainline 1)
• Zones: Which zones were running when the variance occurred (e.g., zones 13, 25, and 37)
• Variance threshold versus actual: The allowed variance percentage compared to the actual variance detected (e.g., 20% versus 33.1%)
• Expected versus actual flow: The flow rate the controller expected compared to what it actually measured in gallons per minute (e.g., 35 GPM versus 26.1 GPM)
• Zone shutdown status: Whether zones were shut down as a result

What Happened

In this example, the controller expected a combined total of 35 GPM from all three valves running on Mainline 1 (zones 13, 25, and 37), but the actual flow measured was only 26.1 GPM. The controller did not shut down any zones because this was configured as an alert-only notification on this site.

Only zones connected to Mainline 1 are affected. Other mainlines, such as Mainline 2, continue to operate normally and are not impacted by this variance.

Common Causes

Several issues can trigger a mainline low flow variance alert:

• Flow restriction on the mainline: An obstruction or blockage in Mainline 1 itself
• Zone valve issues: A zone valve connected to Mainline 1 may not be opening fully or may be obstructed
• Pump problems: On systems with a pump, there may be low flow from the pump or an issue with pump performance or the pump intake
• Configuration settings: The flow variance limit may be set too low for the system's normal operating conditions
• Disabled shutdown feature: The flow variance shutdown feature may be disabled, resulting in alerts only rather than automatic zone shutdowns

Interpreting Variance Measurements

The variance threshold is measured as a percentage. In the example message, the controller was configured to allow a 20% variance but actually detected a 33.1% variance, which exceeded the threshold and triggered the alert.

The expected and actual flows are measured in gallons per minute (GPM). The controller expected 35 GPM from zones 13, 25, and 37 running simultaneously, but only measured 26.1 GPM in actual flow.

This is specifically a low flow variance, meaning the actual flow was lower than expected, not higher.

Troubleshooting Steps

When investigating a mainline low flow variance, check the following:

1. Inspect the mainline for obstructions or blockages that could be restricting water flow.

2. Examine the zone valves connected to the affected mainline to ensure they are opening completely and are not obstructed.

3. If your system uses a pump, check pump performance and inspect the pump intake for any issues that could reduce flow.

Adjusting Flow Variance Settings

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 systems.

3. Adjust the variance percentage as needed based on your system's performance and characteristics.

Using Advanced Flow Variance

Advanced flow variance allows you to set different variance percentages for different expected flow ranges, providing more precise control for systems with varying flow demands.

1. Access the Advanced Flow Variance settings in the Flow Management section.

2. Configure different variance percentages for different flow ranges.

For example:

• When the controller expects 25 GPM of combined zones, set a 30% variance to allow for greater fluctuation at lower flows
• When the controller expects a combined total of 300 GPM from the zones, set a tighter variance of just 5% since higher flows should be more stable and predictable

This approach accounts for the fact that lower flow rates may naturally have more variability, while higher flow rates should be more consistent.

Enabling Automatic Shutdown

Consider enabling the controller to shut down zones automatically when low flow variance limits are exceeded. This provides both a message notification and an automatic shutdown response if the variance threshold is exceeded, helping to prevent potential damage or water waste from continued operation during abnormal flow conditions.

Video Walkthrough

Video originally published July 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.