Is maintaining chlorine at 50 ppm for 24 hours sufficient for ensuring a domestic water system is Legionella-safe long-term?

Maintaining chlorine at 50 ppm for 24 hours is not sufficient for ensuring that a domestic water system is Legionella-safe in the long term. While high levels of chlorine can effectively kill Legionella bacteria in the short term, they do not provide lasting protection. After the chlorine is removed or dissipates, the conditions for Legionella growth can return if there are favorable factors present, such as water stagnation, warm temperatures, or biofilm development.

In general, ongoing management strategies are necessary to control Legionella risk, which may include regular monitoring, maintaining appropriate water temperatures, and implementing routine flushing of systems that aren't frequently used. Therefore, while elevated chlorine levels can be beneficial as part of an immediate response to a suspected contamination event, they do not solve the underlying conditions that could allow Legionella to thrive over time.