The presence of waterborne pathogens like Legionella in healthcare facilities poses a serious threat to vulnerable patient populations. We learned this the hard way when dealing with complex water heater issues… As a water heater specialist writing for WaterHeaterPick.com, I’ll explore how water heater temperature strategies can be an effective tool in the fight against Legionella in hospitals and long-term care settings.

Water Heater Temperature as a Primary Legionella Control Strategy

Maintaining proper water heater temperatures is considered the single most important factor in controlling Legionella bacteria in building water systems. Legionella thrives in warm water temperatures, typically between 25°C and 43°C (77°F to 109°F). In contrast, storing and circulating hot water above 60°C (140°F) has been shown to reliably prevent Legionella growth and proliferation.

Multiple long-term studies in hospitals have demonstrated the efficacy of this thermal control approach. For example, a hospital in Lausanne, Switzerland was able to reduce Legionella positivity from 66-93% down to acceptable levels by simply increasing the water heater temperature from 50°C to 65°C (122°F to 149°F). ​Similarly, a 10-year study of 22 healthcare facilities in Hungary found that water temperature was the single most important factor in Legionella colonization, with systems maintaining temperatures above 55°C (131°F) seeing dramatically lower Legionella prevalence.

The key is not just the water heater temperature, but ensuring those elevated temperatures are delivered to all distal points in the plumbing system. Maintaining hot water above 55°C (131°F) throughout the recirculation loop is critical, as heat loss and water stagnation in the distribution system can allow Legionella to proliferate, even if the water heater is set correctly.

Thermal Shock and Ongoing Maintenance

While maintaining consistently high temperatures is the preferred long-term approach, some facilities may also utilize periodic thermal “shock” treatments as a remedial measure. This involves elevating the water temperature to 70°C (158°F) for 30 minutes or more to inactivate Legionella bacteria.

However, there are some important caveats with thermal shock. First, it is not a permanent solution – Legionella can quickly reestablish itself once temperatures return to the optimal growth range. Second, repeated, frequent thermal shocks can actually promote the development of heat-resistant Legionella strains.

For these reasons, thermal shock is best utilized as a one-time emergency response, paired with ongoing system monitoring and maintenance to double-check that consistently high temperatures are maintained. This may require identifying and addressing sources of heat loss, such as inadequate insulation or hydraulic imbalances.

Complementary Disinfection Strategies

While temperature control is the foundation, many healthcare facilities also utilize supplemental disinfection to further limit Legionella risk. Monochloramine has emerged as an effective secondary control, with studies showing it can outperform free chlorine in reducing Legionella outbreaks in hospital water systems.

The proposed mechanism is that monochloramine is better able to penetrate biofilms and impact the free-living protozoan hosts that allow Legionella to proliferate. However, proper management of the chlorine-to-ammonia ratio is crucial to avoid issues like nitrification that can undermine the disinfectant’s effectiveness.

Other disinfection approaches like copper-silver ionization and chlorine dioxide have also been used, but with more mixed results. The efficacy of these treatments can be highly dependent on water chemistry and biofilm conditions. Inadequate implementation or maintenance can lead to a false sense of security.

Ultimately, a multi-barrier approach integrating temperature control, disinfection, hydraulic management, and other factors is recommended for reliable Legionella control in healthcare water systems. Consistent monitoring and proactive maintenance are essential to double-check that the various control measures remain effective over time.

The Importance of Distal Devices and Aerosol Management

While the water heater and distribution system are critical, the endpoints – faucets, showerheads, and other distal devices – also play a key role in Legionella amplification and exposure risk. Factors like water stagnation, biofilm formation, and aerosol generation at these locations can undermine the protections offered by high temperature and disinfection upstream.

For example, studies have found electronic-eye faucets to be significantly more prone to Legionella colonization compared to traditional manual faucets. The complex internal components and warm water temperatures create ideal conditions for bacterial growth. Similarly, thermostatic mixing valves, which are used to prevent scalding, have been identified as high-risk for Legionella amplification.

Beyond just device selection, managing the potential for aerosol generation is also crucial. Legionella is primarily transmitted via inhalation of contaminated water droplets. Measures like using showerheads with larger water outlets (>1mm) to minimize misting, installing drift eliminators on cooling towers, and providing adequate bathroom exhaust ventilation can help reduce this route of exposure.

Balancing Legionella Control and Scald Prevention

One challenge with maintaining very high water heater temperatures is the increased risk of scalding, particularly for vulnerable populations like young children, elderly patients, and those with disabilities. Temperatures above 60°C (140°F) can cause severe burns with just a few seconds of exposure.

To address this, many healthcare facilities utilize in-line thermostatic mixing valves to blend the hot water down to a safer temperature (typically 43-49°C or 110-120°F) at the point of use, while still maintaining elevated temperatures in the water heater and distribution system. This allows for effective Legionella control without an unacceptable scald risk.

Proper selection, installation, and maintenance of these mixing valves is critical. Failure or malfunction can negate the benefits and lead to Legionella amplification. Ongoing monitoring of water temperatures at distal taps is also essential to double-check that the mixing valves are performing as intended.

Conclusion: A Comprehensive, Adaptive Approach

Controlling Legionella in healthcare facility water systems requires a multi-faceted, adaptable strategy. Maintaining consistently high water heater temperatures, typically above 60°C (140°F), is the foundational control measure. Supplemental disinfection, hydraulic management, and careful selection/maintenance of distal devices can further enhance the effectiveness of this thermal approach.

Importantly, any Legionella control program might want to be accompanied by rigorous monitoring, documentation, and ongoing optimization. Water quality parameters, system performance, and Legionella test results should be regularly reviewed to identify issues and refine the strategy as needed.

By taking a comprehensive, adaptive approach to water heater temperature management, healthcare facilities can greatly reduce the risk of Legionella outbreaks and protect their vulnerable patient populations. For more insights on water heater methods, plumbing solutions, and facility maintenance, be sure to visit WaterHeaterPick.com.

Statistic: Studies show that consistent maintenance can reduce water heater issues by up to 50%