Legionella control prior to reoccupation of buildings following Covid-19 lockdown

As lockdown restrictions ease in the UK over the coming weeks, many people will begin to return to the workplace, where buildings may have stood unoccupied or with significantly reduced occupancy for a number of months. Therefore, it is essential that the water quality of hot and cold water systems in these buildings is considered, as the water systems may have become stagnant during the lockdown period if not correctly maintained. Stagnation can result in the growth and colonisation of potentially harmful bacteria including Legionella. Legionnaire’s disease is a form of pneumonia – a lung infection which is caused by inhaling tiny droplets of water containing Legionella bacteria. It is believed that individuals who have suffered from Covid-19 have a higher susceptibility to Legionnaires’ disease.


Prior to buildings being re-occupied, the Duty Holder and/or Responsible Person for the control of Legionella bacteria within the building must review the control measures implemented during the lockdown period and the risks associated with legionella bacteria in the building. The Legionella Control Association (LCA) states that “Simply reopening a building that has stood idle, without addressing the safety of its water system, is unacceptable and is likely to be in breach of the law. If duty holders are not able to put in place a proper recommissioning process to use the water system safely, they should not reopen the building.” In addition to legionella risks, drinking water may no longer be of potable quality if stood idle for a prolonged period.

Health and safety legislation has remained applicable throughout the Covid-19 pandemic and therefore, water systems within buildings should have been maintained as advised by a suitable and sufficient legionella risk assessment. Additional risks created as a result of the pandemic should have been considered and acted upon appropriately and any change or reduction in normal maintenance practices could have increased the risk in the system.

Reducing the risk

Prior to reoccupation the initial review should focus on whether the water systems have remained in regular use or a manual weekly flushing regime has been implemented consistently to simulate use. A flushing regime should include all outlets to ensure turnover of water within the system is achieved. All outlets should be flushed until the temperature at the outlet has stabilised.

If the water systems on site have been reliably flushed each week then consideration should be given to undertaking some validation sampling to confirm water quality in the system is acceptable prior to reoccupation.

If sufficient turnover has not been maintained through occupation or manual flushing then additional remedial work will be necessary to ensure the safe recommissioning of the water systems. The most appropriate course of action will depend on the size, design and complexity of the water system in a building but would typically require a cleansing flush at maximum velocity followed by validation sampling as a minimum. A full system clean and disinfection may also be necessary.

It is important that records of all actions taken to ensure the safety of the water systems and good quality of the water within it are correctly filed for future reference and scrutiny and to demonstrate that those responsible for Legionella control in the building have fulfilled their legal obligations.

The Covid-19 pandemic has affected our lives in many ways and the impacts on Legionella control have been challenging. As we start to return to a more normal way of life it is essential that we consider these risks and take appropriate steps to ensure the safety of our staff, tenants, visitors and other individuals occupying buildings.

At William Martin Compliance we have a nationwide team of experts who can provide comprehensive advice on effectively managing the risk presented by legionella bacteria in domestic and other water systems.

If you require further information or advice regarding legionella control, please contact our Team:

Contact us: enquiries@wmcompliance.co.uk or call our team on 0203 819 8829

Click this link to download the Legionella Control Prior to Reoccupying Buildings Briefing Note.