Planning for the Return to work – Legionella Risks

As a result of the UK lockdown in response to the coronavirus pandemic many buildings have been closed and unoccupied for several weeks. When businesses start returning to work and buildings are reopened several factors need to be considered; these are being considered in a series of blog articles posted on this site. One risk factor to be considered is that of Legionella.

The closure of buildings including offices, hotels and a range of other buildings may have increased the risks from Legionella when the buildings are reoccupied.  This increase in risk arises because water systems have not been used during the lockdown, meaning there has been very little turnover of hot and cold water within the systems. This may lead to the proliferation of Legionella bacteria within the water systems.

Building controllers and employers need to consider the risks posed by Legionella and need to take appropriate actions to control or mitigate those risks. Such steps may include:

• Running the water system (hot and cold) at least once a week.
• Running shower heads and taps frequently (ideally at least weekly).
• Draining the water systems fully if buildings are to remain unoccupied for long periods.
• Continuing to clean and descale shower heads and hoses.
• Ensuring that when hot water is stored, the hot water storage cylinders store water at 60°C or higher.
• Checking that hoot water is distributed at 50°C or higher (with thermostatic mixer valves fitted as closely as possible to outlets where a scald risk is identified).
• Ensuring that the cold water is stored and distributed below 20°C.
• Continuing to remove dead-legs from the water system.

Where premises have cooling towers that have been switched off, these should be checked by a competent person before the system is switched back on.

We also have a blog post on the Control of Legionella