The Silent Reservoir: Uncovering the Hidden Peril in Tower Equalization Lines

Cooling towers are vital to large buildings, from hospitals and healthcare complexes to expansive university campuses. They help remove heat from water, which then recirculates to chillers or other equipment. However, hidden in these systems is a significant yet often overlooked threat: stagnant water harboring Legionella bacteria. One key culprit is the equalization (EQ) line, a large-diameter pipe designed to balance water levels among multiple tower sumps.

The Cooling Tower Basics

Cooling towers operate by allowing water to flow over specialized media, exposing it to airflow and promoting evaporation. This process cools the water, which then returns to the building’s systems. Because the water is continually cycled, proper water treatment—including biocides and corrosion inhibitors—is essential. Even minor oversights can lead to serious problems, particularly when it comes to low-flow or no-flow areas.

Equalization Lines: Essential but Overlooked

In multi-tower setups, each cooling tower has a sump that collects and stores water. An EQ line, sometimes 30 inches or more in diameter, connects these sumps to ensure water flows from one tower to another when levels become imbalanced. Ideally, this prevents overflow in one sump while another runs low.

However, many buildings have variable load demands, meaning one tower might operate heavily at certain times while another is partially idle. When water isn’t actively flowing through the EQ line for extended periods, it becomes stagnant, creating an environment where Legionella can flourish. The size of these lines—often several feet in diameter and dozens of feet long—exacerbates the problem by holding large volumes of water at relatively warm temperatures.

How Stagnant Water Fuels Legionella

Legionella pneumophila thrives in water between 68°F and 122°F, a temperature range commonly found in cooling systems. When water remains still, biocide levels drop, and biofilms form on interior surfaces. These biofilms act as protective layers for microbes, making them harder to eliminate once established. In a large EQ line, residual disinfectants may never penetrate deeply enough to kill embedded bacteria.

If the water in this pipe stays motionless for days or weeks, it can become a concentrated breeding ground for harmful pathogens. When flow eventually resumes—perhaps because another tower comes online—this stagnant water can surge into the active cooling loop, carrying a potentially high bacterial load. Even well-maintained systems can be caught off guard by this sudden contamination event.

The Facility Manager’s Dilemma

For healthcare facilities, the stakes are particularly high. Patients, including those with weakened immune systems, are more susceptible to infections like Legionnaires’ disease. An outbreak linked to a hospital’s cooling system can lead to strict regulatory scrutiny, legal liabilities, and a damaged reputation.

Universities also face risks. Large campuses often rely on multiple cooling towers to serve various buildings. Uneven usage across these towers can easily result in stagnant sections of piping, which, if ignored, become a hidden reservoir of bacteria. Managing these issues proactively saves resources in the long run, as emergency shutdowns and costly decontamination protocols can have serious financial and operational impacts.

Spotting and Preventing Stagnation

Monitoring is critical. Regular water testing, temperature checks, and inspections of flow rates help facility managers identify trouble spots. Although daily flushing or draining might seem excessive, scheduled purges can keep water from lingering in dead zones. Some buildings opt for automated drain valves or timer-based flushing to ensure water moves frequently enough to prevent bacterial buildup.

Yet the primary challenge isn’t necessarily installing new equipment. It’s raising awareness and integrating the EQ line into the broader water management plan. By recognizing how essential these large-diameter connections are—and how vulnerable they can become—facility teams can take targeted steps to control risks. This often involves collaborating with water treatment specialists, adopting a rigorous maintenance schedule, and ensuring staff are trained to spot early warning signs of biofilm or bacterial growth.

Looking Ahead

Cooling towers remain a central piece of modern infrastructure, but the EQ line—hidden, yet crucial—deserves closer attention. Proactive measures, from more frequent testing to improved design and monitoring, can significantly reduce the risk of Legionella. Safeguarding occupants, patients, and staff is not just about maintaining a functional cooling system; it’s about recognizing and managing the subtle threats that can lurk within complex water networks—particularly those as large and under-monitored as the equalization line.

How Chemstar WATER Can Help

At Chemstar WATER, we recently installed specialized equipment for a major hospital client to periodically drain the EQ line and cycle the water, preventing stagnation and reducing the risk of Legionella. If you’re concerned about similar issues at your facility, we can provide practical solutions backed by years of experience in water treatment and system optimization. Contact us for this or any other water treatment needs.