Legionella Build-Up in Unoccupied Buildings

Vacant properties in the UK are at risk from water-borne health threats, as the neglect of hot and cold-water systems can lead to water stagnation. All buildings should be carefully managed to prevent this happening during periods of non-occupancy, whether they are vacant homes or public facilities. Healthcare centres, schools and guest houses are good examples of buildings that carry a high risk. By using water outlets such as taps once a week, or by implementing water-system flushing on a regular basis, a safer degree of water flow can be established in vacant properties and so minimise the chances of stagnation occurring.

Dangerous bacteria such as legionella should be better understood and factored into planning by building owners and managers to prevent its spread. Recent incidences have resulted in public prosecutions, many of which have been reported in the media on a local and national scale. In 2018, Public Health England recorded over 750 outbreaks of Legionnaires Disease, which is caused by the inhalation of contaminated water droplets. Elderly or infirm individuals are particularly at risk of infection, as the disease attacks impaired immune systems, and symptoms can often be misdiagnosed as flu or pneumonia.

Building managers are legally required by The Control of Substances Hazardous to Health regulations to make their property safe for occupancy, and so fulfil their responsibilities in controlling any legionella build-up. This should include full risk assessments to test for bacteria in hot and cold water systems, and the appointment of a Responsible Person capable of reporting / dealing with the issue, should any trace of legionella be detected. Any scheme undertaken to control the risk must be managed to the Approved Code of Practice L8 within HSG 274 or Health Technical Memorandum (HTM) 0401.

Empty or neglected buildings are at such great risk because legionella bacteria can linger and survive in pipework, particularly where the water in the system has been allowed to stagnate. Deadly legionella bacteria can then pose a health risk to any new occupiers, visitors to the property or any workers. Even partial neglect to a building, such as during a construction or refurbishment project, or in facilities with multiple water outlets, can negate any previous good work and allow standing water to become affected. In such cases, fresh risk assessments are required to ensure that water systems are safe before any exposure to the general public. A pipe flushing regime is imperative to maintain the flow of water and prevent any legionella build-up.

Should a legionella risk be identified in a vacant property, it is necessary under ACOP L8 guidance for the duty holder to appoint a Competent Responsible Person capable of preparing and overseeing a written scheme to control the situation. This individual will be able to assess the risk of infection and the type of water system in the building, as well as managing all workers and ensuring that they are able to carry out all checks safely.