Pump drawdown monitoring is one of the most powerful tools a wastewater utility has for understanding the health and efficiency of its lift station pumps. Drawdown refers to the rate at which a pump lowers the liquid level in the wet well during a pumping cycle. Tracking this rate over time provides a direct measure of each pump’s performance. A declining drawdown rate over time can signal a host of problems, such as worn impellers, clogged suction lines, or even issues with force main capacity, long before a failure occurs. Because of its importance, many utilities rely on manual drawdown tests. This practice can be both labor-intensive and limiting when compared to more frequent monitoring based on virtual drawdown testing.
The Challenges of Manual/Field Drawdown Testing
Manual drawdown tests typically involve isolating a pump, recording the wet well level, starting the pump, and timing how long it takes to lower the liquid to a set point. Operators then calculate the flow rate using the known wet well volume. While this method can yield somewhat accurate results for that moment in time, it has significant drawbacks. First, it requires staff to be on site and often to take pumps in and out of service. Scheduling tests around low flow periods, typically in the early morning hours, exposes operators to unsafe working conditions. Weather events, peak usage, or staff availability can all delay or complicate testing.
Even when performed perfectly, a single manual test provides only a snapshot of pump performance. Pump wear gradually grows, and problems such as partial blockages or subtle impeller erosion may develop over weeks, months, or even years. If drawdown is measured once or twice a year, small but significant changes can go unnoticed until they escalate into reduced pumping capacity or complete failure. Furthermore, wet well conditions can vary hour to hour; a one-time test might not reflect typical or worst-case operating conditions.
Data-Based Drawdown Analysis
Data-based pump drawdown analysis enables utilities to continuously monitor pump performance, even with limited data, capturing detailed information that manual testing simply can’t match. Every pump cycle contributes to a long-term performance record, revealing trends, seasonal changes, and the effects of maintenance activities. Instead of relying on occasional snapshots, utilities gain a comprehensive view of pump health, enabling earlier detection of issues and more informed decision-making.
Benefits to Utilities
This shift not only improves efficiency but also enhances safety and resource management. Crews spend less time on routine field testing and more time focusing on proactive maintenance. Utilities can respond faster to emerging issues, strengthen their capital planning, and reduce the risk of costly emergencies and sanitary sewer overflows.
Conclusion
In today’s environment of aging infrastructure and rising performance expectations, the move from manual drawdown testing to continuous monitoring is not just a technological upgrade; it is a fundamental improvement in how utilities manage and protect their wastewater systems. By embracing long-term drawdown analysis, utilities gain a powerful, data-driven means to ensure reliable pump performance and safeguard the communities they serve.
For more information, please contact Chad Morris at cmorris@arudrra.com or Manal Alduraibi at malduraibi@ardurra.com.
Be sure to check out our recent blog on influent flow and SSOs, and watch for our next post covering I&I challenges and effective strategies to overcome them.
