Legionella mitigation solutions from Watts

Legionella solutions for your facility
Treat the conditions, not just symptoms

solutions graphics with showerhead

With a more thorough understanding of the underlying conditions that put your facility at risk, you can prescribe an effective water management program. The following provides you the broad range of potential solutions: at the points of source, points of use, and the points of condition within. Watts provides a comprehensive solution set for your water management plan, including Legionella and scalding mitigation throughout your water system. To properly address the specific needs of your facility you will want to consult with a specialist.

Domestic Hot Water

The risk of Legionella growth in domestic hot water can be mitigated by elevating the water to high temperatures, or by ensuring it remains in a constant state of flow. Tankless water heaters generate domestic hot water using advanced flow control to keep water constantly moving thereby severely reducing any chance of bacterial growth. Tank water heaters generate domestic hot water and store it at 140°F creating an inhospitable environment for Legionella to breed. Both options will make it easy for your facility to comply with ASHRAE Guideline 12-2000 and ASHRAE Standard 188-2015.

legionella growth chart
Tankless AERCO hot water heater
AERCO Innovation high-efficiency water heaters deliver precisely controlled instantaneous hot water without storage.
High-efficiency PVI hot water heater
PVI Conquest water heaters provide 140° F temperature water with up to 97% thermal efficiency.


While heating water daily to 140° F is one of the most effective and reliable control measures for dealing with Legionella, it is too hot for people. On average, any water that is above 106° F can cause pain in humans while water that is 140° F can cause third degree burns in a matter of seconds. This is why plumbing codes limit the maximum temperature exiting a fixture at 120° F with the expectation that people can readily control the mix of cold and hot water at the faucet to meet their needs.

The solution to this competing set of interests is found in the use of tempering valves or mixing valves that blend hot water (generated and stored at temperatures high enough to kill bacteria) with cold water in a controlled manner. This ensures constant, safe outlet temperatures while minimizing the occurrences of both scalding and legionella.

A point-of-source (POS) system locates valves at or near the water-heating source and typically has a higher capacity for controlled temperature water.

A point-of-use (POU) system uses multiple, smaller mixing valves at or near plumbing fixtures such as showers, lavatories, whirlpools, and emergency fixtures to minimize the risk of scalding. Both types are common and have a range of standards issued by the American Society of Sanitary Engineers (ASSE) relevant to particular usage.

Intellistation® is a digital mixing solution that provides quick and easy documentation, delivers water within ±2° F of set point, and simplifies hyper-heat sanitation. Intellistation® documents activity, simplifying meeting the requirements of a CMS water quality management plan.
Powers products
Combine mixing products from Powers with Intellistation® to ensure fixture temperatures are comfortable and safe.

Ultraviolet Light

Ultraviolet (UV) disinfection systems are highly effective at providing protection against microbiological contamination in water, including Legionella. Making sure the lamp strength is adequate to kill Legionella should be your top priority when selecting a UV solution. One should also take measures to reduce sediment in the water to increase the efficacy of UV through the use proper filtration and anti-scale equipment, such as the Watts Big Bubba and OneFlow™ models.

SmartStream™ UV is an example of highly effective ultraviolet disinfecting systems.

Filtration and Scale Reduction

Water filtration can improve the water systems’ Legionella risk-reducing ability by preventing the build-up of sediment and scale upon which bacteria thrive. In addition, filtration helps maintain the operating efficiencies of boiler, hot water heater, and UV systems.

Hard water minerals can cause scale deposits inside pipes, valves and other system components. Template Assisted Crystallization (TAC) is an environmentally friendly solution for preventing scale build-up.

Learn more about this salt-free, scale-prevention technology.

OneFlow™ Anti-Scale Systems reduce scale and maintain operating efficiency of boiler and hot water heater systems.
Big Bubba
Big Bubba Commercial Filtration high volume systems remove sediment with cleanable and reusable micron mesh cartridges.

Copper-Silver Ionization

According to Janet Stout, Special Pathogens Lab, “Copper-silver ionization is a disinfection method that is used to eradicate Legionella from hot water recirculating systems. Disinfection with ionization occurs when the positively charged copper and silver ions released from the ionization system bind to the negatively charged cell wall of Legionella causing cell death.” Copper-silver ionization is known to be very effective in Legionella control however this solution has higher capital and maintenance costs than other methods. Most states require a certification in order to work with this solution.

Chemical Treatment

Chlorine is proven to be very effective in reducing the risk of Legionella. Most often it is injected after the municipal water supply has entered the building in the mechanical room. Other chemicals may be used instead of chlorine but chlorine is most widely accepted by the industry. However, chlorine and other chemicals can prove to be health risks if levels are outside of accepted parameters. In addition, chlorine is very corrosive to equipment and piping in the water management system, with the potential to cause pinhole leaks.

Piping and Drainage

Outbreaks of Legionella bacteria, which can cause Legionnaires’ disease, are a particular concern at healthcare locations such as hospitals, nursing homes, and long-term care facilities. The potential for a widespread outbreak is also a challenge for buildings in the hospitality industry, such as hotels, motels, and resorts.

piping and drainage image
Blucher Piping and Drainage is constructed of smooth stainless steel so it does not harbor bacteria.

Backflow Systems

Backflow is defined as the reverse flow of contaminated or undesirable substance into the potable water supply. Installing a backflow preventer can protect the water supply from this very serious type of situation.

backflow valves
Watts Backflow Systems prevent the reverse flow of polluted water from entering the potable water supply due to backsiphonage or backpressure.