In which part of the domestic water system can you expect the highest risk for Legionella proliferation?

Hot water storage tanks present the highest risk for Legionella proliferation due to the specific temperature range that supports the growth of this bacterium. Legionella thrives in water temperatures between 68°F (20°C) and 122°F (50°C), with the optimal growth temperature being around 95°F (35°C). Since hot water tanks are typically set to maintain temperatures that are conducive to bacterial growth, they can become a breeding ground for Legionella if not properly managed.

Additionally, hot water tanks often store water for extended periods, which provides ample opportunity for Legionella to multiply if conditions are favorable, such as stagnant water or low disinfection levels. Regular monitoring and maintenance, including temperature control and system disinfection, are essential to mitigate this risk.

In contrast, cold water storage tanks typically maintain cooler temperatures that are less favorable for bacterial growth. Drainage systems do not contain standing water at warm temperatures conducive to Legionella, and direct to fixtures, while they can be a concern, provide less opportunity for bacterial proliferation compared to dedicated hot water storage tanks. Thus, it is clear that hot water storage tanks represent the highest risk environment for Legionella growth within domestic water systems.