Outbreaks of Legionnaires’ disease have been associated with situations – water main breaks, construction, opening of backup water feeds – that have presumably sent contaminants into a building domestic (potable) water system or dislodged biofilm from piping. Such situations are sometimes evidenced by discolored water.

Responding promptly and effectively to such events might prevent a Legionella-associated illness or death. Your Legionella HACCP water plan should therefore include measures to take in various situations.

The plan must be specific so that you can respond quickly. For example, if a water main break near your facility occurred today, would you be able to immediately implement protective measures appropriate for the situation? If you would have to spend a few hours searching the Internet and making phone calls to determine what to do and where to get help, your plan is not specific enough.

In general, the plan should outline what to do in the event of discolored water in part of the building, discolored water throughout most of the building, water main work, water system shutdowns of various durations (e.g., < 24 hours; 1 to 5 days; 6 to 30 days; > 30 days), and boil-water advisories.

Flushing can be performed with the objective of ridding the system of potentially contaminated water while minimizing transmission of water to people, especially people vulnerable to infections. Chemical disinfection will be appropriate in some cases, either at high levels for a few hours while restricting water use, or at low (ingestible) concentrations over a few days with normal water use. In hospitals and nursing homes, protective measures might include water restrictions or the installation of point-of-use filters rated for ≤ 0.2 micron.

Even in buildings with excellent plumbing system maintenance and continuous domestic water disinfection, preparing to respond quickly to these incidents is crucial for preventing Legionnaires’ disease.

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