Five Building Changes That Should Trigger a Legionella Review

Many duty holders understand the importance of having a Legionella risk assessment in place, but fewer realise that changes to a building or its use can significantly alter the level of risk within a water system. As a result, an assessment that was suitable a year ago may no longer accurately reflect current conditions.

Legionella bacteria can multiply when water systems experience changes in temperature control, water usage patterns, storage arrangements, or occupancy levels. For this reason, any significant alteration to a building should prompt a review of existing Legionella control measures.

Here are five common building changes that should trigger a Legionella review.

1. Office Refurbishments
2. Changes in Occupancy
3. Installation of New Water Heaters
4. Temporary Building Closures
5. Converting Spaces for Different Uses

1. Office Refurbishments

Refurbishment projects often involve changes to plumbing systems, washrooms, kitchens, or building layouts. During construction work, sections of pipework may be removed, extended, isolated, or left unused for extended periods.

These changes can create conditions that encourage bacterial growth, including:

• Water stagnation in redundant pipework
• Altered water temperatures
• Dead legs within the system
• Reduced water turnover at outlets

Even relatively minor refurbishment work can affect the performance of a water system. Once work is completed, a Legionella review can help identify any new risks and ensure the system remains compliant with current guidance.

2. Changes in Occupancy

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