Covid-19 Pandemic & Water Installations: a Legionella Contamination Risk?

During the 2020/21 pandemic many buildings including hotels, schools, universities, student accomodation blocks, fitness and leisure centers have been closed for several months. This change in normal function of the building means an automatic change in the operation of the water installation and its use, meaning less or no water usage leading to water stagnation. Flowing water and appropriate temperatures (potable water hot (PWH) > 60 °C and potable water cold (PWC) < 20 °C), materials of construction in the water installation, chemicals and additives as well as particle debris are the ‘usual suspects‘ of microbial contamination of water installations. All these factors significantly contribute to the microbial quality of water. Even if only one of these factors is out of control, the risk of contamination can significantly increase.   Water stagnation (water usage is low or not present) occurs when buildings are not operating as intended. The immediate measure to avoid microbial contamination is regular flushing (ideally daily) to imitate normal water operation. Daily flushing of each outlet in a building is challenging, requires resources, and needs consistent strong management together with robust record keeping and documentation. Alternatively, the water installation has to be drained and refilled according to the Code of Practice. Refilling a water system should be carried out as close as possible (< 48 h) prior to reopening and exposure to users. Not only have we seen high numbers of the above mentionedbuilding types change their regular operation during the pandemic, but so have many healthcare buildings and ones repurposed for healthcare. For example, some hospitals have changed their use of specific wards, e.g., to accommodate extended Intensive Care Unit (ICU) bed capacity.  Exhibition halls and hotels have been repurposed to extend ICUs etc. Every change in building operation poses a risk to microbial water quality, for example; an orthopedics unit which has been repurposed to an ICU will have a different operation of its bathrooms. Orthopedic patients are often capable of moving and showering in the bathroom, but ICU patients are normally not using bathroom or showering. Such a change in operation can result in stagnation due to the limited outet use. Every part of the water installation is physically connected and communicates at a microbial level with the overall system: Microbes growing in one site of the system are capable of moving in all directions – upstream as well as downstream – and can colonise other areas of the system. Stagnating water in just a few outlets of a large installation has been  repeatedly shown to lead to Legionella, Pseudomonas and other pathogen contamination of a complete water system. Remediation of such contamination takes many months, or even years, to be successful. The ESCMID Study Group for Legionella Infections – ESGLI ( have published recommendations with valuable information and guidance on how to deal with the water installation of the respective building category during the pandemic. They are free to download from; Would you like to know more about how to avoid or manage these situations during the Covid-19 pandemic? Legionella contamination Legionella outbreak Pseudomonas contamination Pseudomonas outbreak Contamination with or outbreak of other waterborne pathogens If you would you like support in managing your water installation to ensure the provision of safe water to users as well as compliance with the Code of Practice, please contact us at:

Covid-19 Pandemic & Water Installations: a Legionella Contamination Risk? Read More »