What Is a Legionella Risk Assessment and Who Legally Needs One?
Legionella is one of those compliance areas that a lot of businesses know they should be thinking about but have never quite got to grips with. The rules are not especially complicated once they are explained properly, but the consequences of getting them wrong are serious enough to be worth understanding clearly. Here is a straightforward overview of what is actually required and who it applies to.
What Is Legionella and Why Does It Matter?
Legionella bacteria occur naturally in water sources and can multiply rapidly in man-made water systems, particularly where water sits at temperatures between 20 and 45 degrees Celsius, or where there is stagnation, scale or biofilm present. When contaminated water is aerosolised and inhaled, it can cause Legionnaires' disease, a potentially fatal form of pneumonia.
The HSE's legionella guidance is clear that the risk is entirely manageable with proper controls in place, but those controls need to be identified, implemented and recorded.
Who Has a Legal Duty?
The legal duty falls on the "dutyholder," which is typically the employer, building owner or person with overall responsibility for a premises. If you manage or are responsible for a commercial property with a water system, that duty almost certainly applies to you. This includes:
- Office buildings and business premises — hot and cold water systems in most commercial buildings require assessment.
- Hotels, leisure facilities and gyms — higher risk due to complex water systems, pools and high footfall.
- Landlords of commercial property — if you let premises to a business, the duty to assess may sit with you depending on your lease arrangement.
- Schools, hospitals and care homes — considered higher risk due to vulnerable occupants and are subject to more stringent monitoring requirements.
- Smaller premises — even a simple hot and cold water system in a small office can require assessment if the risk warrants it.
Domestic landlords also have responsibilities, though the level of risk and required action in a standard residential property is generally lower.
What Does a Risk Assessment Actually Involve?
A legionella risk assessment involves a competent person surveying the water systems on the premises to identify any potential sources of risk. This includes checking water temperatures, identifying areas of stagnation or deadlegs in pipework, reviewing the condition of storage tanks, and assessing any cooling towers or other risk systems. The output is a written report that identifies the risk and sets out the control measures required.
Following the assessment, those control measures need to be implemented and documented. This is where a site logbook comes in. Companies like Clean Air UK provide customised site logbooks as part of their water treatment service, ensuring records are structured around the specific tasks and frequencies required for each property. For businesses in the North West, providers such as Centric OR Compliance offer a comparable assessment and monitoring service for organisations managing legionella compliance across their sites.
How Often Does It Need to Be Done?
A risk assessment is not a one-off. It should be reviewed regularly and any time there is a significant change to the water system or building use. Routine monitoring tasks including temperature checks, flushing of infrequently used outlets and tank inspections need to happen at defined intervals and be recorded each time.
The HSE's ACOP L8 is the authoritative guide for all of this. If you have not read it or had a competent person review your systems against it, that is the starting point.
The Bottom Line
If you are responsible for a commercial premises with a water system, a legionella risk assessment is almost certainly a legal requirement rather than a choice. Getting it done properly, keeping adequate records and reviewing controls regularly is what compliance actually looks like in practice.