The effect of a self-regulating trace heating element on Legionella within a shower

Area of Science:

• Microbiology
• Plumbing Engineering
• Public Health

Background:

• Legionella bacteria pose a significant health risk in water systems.
• Showers can harbor Legionella, especially in stagnant water areas like dead-legs.
• Maintaining adequate hot water temperature is crucial for preventing bacterial colonization.

Purpose of the Study:

• To evaluate a self-regulating trace heating element for maintaining shower temperatures.
• To assess the impact of trace heating on Legionella colonization in shower systems.
• To determine the critical temperature thresholds for Legionella growth and eradication in showers.

Main Methods:

• A self-regulating trace heating element was installed in shower mixer valves and dead-legs.
• Temperatures were monitored in the trace-heated components and circulating hot water.
• Legionella colonization levels were assessed in different sections of the shower system.

Main Results:

• Trace heating maintained temperatures of 50°C ± 1.5°C in dead-legs when hot water supply exceeded 45°C.
• Legionella appeared in trace-heated dead-legs when temperatures dropped to 45°C or below.
• Consistent 50°C temperatures eradicated or significantly reduced Legionella; uninsulated mixer valves remained colonized.

Conclusions:

• Self-regulating trace heating is effective in controlling Legionella when consistently maintaining temperatures at or above 50°C.
• Temperature fluctuations below 50°C, even with trace heating, can permit Legionella proliferation.
• Proper insulation of components like mixer valves is essential for effective Legionella control in conjunction with trace heating.