Prepare Your Cold-Water Circulation System and Battle Against Legionella
The COVID-19 pandemic has brought attention to vulnerabilities in plumbing systems, including cold-water systems. Stagnation and warming of unbalanced cold-water systems during building closures have raised concerns about Legionella growth.
When cold water flow is minimal or stopped altogether, as seen during the recent lockdowns that left buildings unoccupied for long periods, disinfectant levels evaporate, and temperatures gradually rise to Legionella’s growth range (77–113°F, 25–42°C), leading to bacteria colonization and uneven free chlorine distribution throughout the system.
Legionella causes a pneumonia-type illness called Legionnaires’ disease and a mild flu-like illness called Pontiac fever. Legionella bacteria can grow and thrive in plumbing systems. When water containing Legionella is used for showers or water fountains, people can inhale or ingest and aspirate tiny droplets of contaminated water, which can lead to infection if the bacteria are present in a dangerous amount.
While much attention has been given to mitigating Legionella in hot water systems, there is a need for proactive measures in cold water systems. “There has been a heightened awareness in the industry focusing on Legionella Mitigation, particularly in domestic water systems,” explains Tom Ruggierio, Director of Sales, Commercial Plumbing, ThermOmegaTech.
The Veterans Health Administration (VHA) has taken a proactive approach in addressing Legionella mitigation in cold water plumbing systems at their Department of Veterans Affairs (VA) medical facilities by planning for “periods of low flow or non-use.”
The VHA 1061(1) directive states, “The use of piping system insulation, automatic drain devices, and recirculation to limit the rate and duration of an increase in cold water temperature in combination with appropriate biocide levels can effectively prevent Legionella growth.”
The Solution: Cold-Water Recirculation
Recirculating cold water eliminates stagnation, which promotes harmful bacteria growth, and provides consistent distribution of residual chlorine throughout the domestic cold-water system.
Keeps water moving
Maintains water quality to reduce stagnation
Ensures residual chlorine is distributed throughout the cold water system
Keeps water temperature in branches and risers evenly distributed, minimizing heat gain
VHA Directive
Balancing Cold Water Systems
“The CircuitSolver® was designed to balance domestic cold-water systems (DCWS) and reduce the risk of bacterial growth,” Ruggierio explains. “Our engineers developed a valve that can dynamically react to the ever-changing conditions that systems may experience. This includes changes in building occupancy, expansion, reduced utilization, and other variables affecting system balance.”
The CSU-CW valve utilizes the same reliable and precise thermal actuator technology as the original CircuitSolver®. It addresses critical issues related to Legionella mitigation in cold water recirculation systems by maintaining a stable temperature. It accomplishes this by continuously monitoring the water temperature and modulating flow to maintain a set temperature at the end of each branch or riser.
The valve operates over a 10°F temperature range. For example, a valve specified for a desired return temperature of 60°F will open at 70°F (10°F above the desired return temperature). At 60°F, the valve is in its closed position. A bypass in the design always allows water to flow back to the pump so that the pump is never dead-headed.
The Use of Thermostatic Technology
ThermOmegaTech® is a world leader in designing and manufacturing self-actuating thermostatic valve technology. They recently turned their attention to battling the Legionella risk in cold water systems.
“The Cold-Water Balancing Valve (CSU-CW) from CircuitSolver® is the market’s first cold water thermostatic balancing valve,” Ruggierio says. “Manual balancing valves could be used, but they are not dynamic and won’t respond to the changing conditions experienced in both hot and cold domestic water systems.”
“CircuitSolver® technology was already an innovative balancing method for domestic hot water recirculation systems, and now there is a solution for cold water systems, too. It’s another step in the right direction to improve plumbing system designs,” Ruggierio says.
“To date, we have provided thermostatic cold water balancing for three VA facilities, with interest from a few others. The more we investigated it, the more we recognized the importance of recirculating cold water. This technology helps to mitigate not only Legionella but also other bacteria and water-borne pathogens from growing. Implementing a cold-water recirculation system is not a nominal task, but what price can one put on a person’s health and safety?” Ruggierio explains. “We are in the early stages of this process. I see interest in this growing over the next several years, expanding from the VA into other healthcare facilities and the hospitality industry.
To achieve stability, system balancing must continually address the ongoing changes occurring within a building. Thermostatic balancing valves adjust dynamically, providing the best opportunity for sustainability and Legionella mitigation.
Stagnant, warm water in a plumbing system increases the risk of Legionella bacteria growth. In cold water systems, adequate flow through high fixture usage and low water temperatures discourage the growth of Legionella and other biofilms. However, in the event flow throughout the system or part of the system is insufficient, standing water can drastically increase the likelihood of bacteria colonization.
When cold water flow is minimal or stopped altogether, as seen during the recent COVID-19 lockdowns that left buildings unoccupied for long periods of time, disinfectant levels evaporate, and temperatures gradually rise in the Legionella growth range, leading to bacteria colonization and uneven free chlorine distribution throughout the system.
Legionella bacteria causes Legionnaires’ disease, a type of pneumonia infecting the lung. People can get sick when they breathe in water droplets or accidentally swallow water containing Legionella.
The CDC says Legionella grows best in a building’s cold water distribution system within a specific temperature range of 77°F-113°F (25°C-45°C). Cold water temperature throughout the system should be maintained at or below 77°F (25°C) to the greatest extent possible to inhibit growth.
CircuitSolver® Union Cold Water Balancing valve.
To discourage Legionella bacteria growth, cold water systems need to be recirculated. They must be balanced appropriately to establish continuous flow and keep line temperatures below 68°F (20°C), the point at which Legionella can begin to colonize.
The Veterans Health Administration (VHA) aims to prevent the spread of healthcare-associated Legionella disease and scald injury from water systems in VHA buildings where patients, residents, or visitors stay overnight with the VHA Directive 1061(1).
The directive states, “The use of piping system insulation, automatic drain devices, and recirculation to limit the rate and duration of an increase in cold water temperature in combination with appropriate biocide levels can be effective at preventing Legionellagrowth.”
The Need for Dynamic Balancing
In order to achieve stability, system balancing must be dynamic – continually addressing the ever-changing conditions. Thermostatic balancing valves adjust dynamically, providing the best opportunity for sustainability and Legionella mitigation. Traditional manual balancing valves could provide a solution to cold water balancing, but their static operation inherently does not factor in nor adapt to the realities of everyday system operation & changes, which may render the balancing obsolete over time.
Utilizing our proprietary thermal actuator as the controlling element, the valve should be installed at the end of each branch or riser in a cold water recirculation system. It will modulate open or closed in response to the water temperature to maintain a specified temperature in the line.
The CSU-CW valve features a union with an optional check valve built into the body of the CircuitSolver® to reduce the number of system components installed and minimize potential leak points.
CSU-CW benefits:
Stainless Steel, which is highly resistant to scaling in high mineral content environments
High thrust actuator keeps orifice free of debris
Union with integrated O-ring for a leak-free seal
Keeps water temperature in branches/risers evenly distributed, minimizing heat gain
Never fully closes, some water always passing through
Provides even distribution of residual chlorine levels
These systems have become more prominent in VA hospitals because of the VHA 1061(1) directive; however, any commercial building such as schools, hotels, high-rise, and multi-family apartment buildings can benefit from implementing a cold-water recirculation system to protect the water lines from the risk of bacteria colonization during periods of low flow or non-use.
Watch how it works and see how the CircuitSolver® Union Cold Water thermostatic balancing valve automatically and continuously balances your cold-water recirculation system to discourage Legionella bacteria colonization and reduce stagnation.
Since its discovery in the summer of 1976, Legionella bacteria has been an ever increasingly hot topic in the plumbing industry, seeming to lurk in pipes and water systems, waiting to strike in a moment of lapsed attention or vigilance.
According to Smithsonian Magazine, the CDC reports that as of 2018, cases of Legionnaires’ Disease, pneumonia caused by aspirating the Legionella bacteria, have risen significantly. With nearly 10,000 cases reported in 2018 alone, Legionnaires seems to be running rampant in modern water systems.
While some attribute the sharp rise in case numbers to improved reporting, awareness, and testing methods, it has also been suggested that aging infrastructure and climate change could be contributing factors.
While prevalent in modern plumbing systems, Legionella bacteria only presents a risk when able to colonize, typically in stretches of piping with warm, stagnant water. For many buildings, simple changes to system design and management procedures can significantly reduce the prevalence of Legionella bacteria and inhibit growth before it can begin.
1. Avoid “Dead Legs” in Piping Design
Minimizing the distance between supply lines and fixtures in your system design can reduce areas of stagnation in the hot water piping which could accumulate scale and biofilm buildup, a prime location for Legionella bacteria to set up shop.
2. Maintain Water Temperature Control
Legionella bacteria flourishes in warm water with comfortable temperatures ranging from around 70°F to 115°F. Storing water at temperatures above 120°F will generally help prevent colonization.
To prevent bacteria growth, specify hot water tanks that store water above 140°F (60°C) and use a mixing valve to recirculate it to the fixtures at 120°F (48.9°C) to comply with anti-scalding regulations.
3. Keep Pumps Running Continuously
Keeping your recirculation pumps running at all times will keep water flowing and prevent bacteria from grouping together and adhering to pipe walls.
4. Perform Routine Maintenance of Equipment
The CDC recommends cleaning water tanks routinely including periodically draining the system to remove scale and sediment. This will prevent biofilm, organic debris, and corrosion from contaminating your water system.
CircuitSolver Sanitary Flush Valve
For domestic hot water systems using a heat-and-flush thermal disinfection method to prevent Legionella bacteria growth, balancing during the flush is essential to ensure thorough sanitation.
CircuitSolver Sanitary Flush Valve utilizes two thermal actuators for automatic thermal balancing of the system; one for normal DHWS operation, and the other for thermal disinfection. Click here to see how it works.
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