The Hidden Impact of Building Changes on Legionella Risk

When people think about Legionella risk, they often focus on the condition of their water systems. However, some of the biggest changes to Legionella risk can arise not from the water system itself, but from changes to the building and how it is used.

A refurbishment project, changes in occupancy levels, the introduction of water-saving measures, or even a shift to hybrid working can all affect water usage patterns and create conditions that encourage the growth of Legionella bacteria.

For duty holders, facilities managers and property owners, understanding the connection between building changes and water hygiene is essential for maintaining compliance and protecting building occupants.

Quick answer: A building change should prompt a Legionella review when it affects the water system, how the system is used, occupancy, water demand, temperature control or the people exposed to the system.

Why Do Building Changes Matter?

Legionella bacteria can multiply in water systems when conditions are favourable, particularly where water temperatures support bacterial growth and water is allowed to stagnate.

Many buildings are continually evolving. Offices are reconfigured, schools expand, healthcare facilities are upgraded, and workplaces adapt to changing employee behaviours. While these projects often improve building performance, they can unintentionally introduce new risks into water systems.

A water system that was considered low risk several years ago may no longer reflect the reality of how the building is currently used.

The Impact of Hybrid and Flexible Working

One of the most significant changes in recent years has been the rise of hybrid working.

Many commercial buildings now experience fluctuating occupancy levels throughout the week. Some floors, departments or meeting areas may see only limited use, resulting in reduced water demand at certain outlets.

When taps, showers or other water outlets are used infrequently, water can remain stagnant within pipework for extended periods. This stagnation can contribute to conditions that increase Legionella risk if not properly managed.

Regular monitoring and reviewing water usage patterns can help identify areas where additional flushing regimes or control measures may be required.