Legionella risk assessment is one of those compliance duties that landlords and property managers know they should have covered but few are clear on exactly how often it needs to be revisited. The answer is not a fixed date in the diary. It depends on your property, your water system, and what has changed since the last assessment was done.

Why summer is the time to act

Water temperature is the key factor in legionella risk. Legionella bacteria thrive in warm water, particularly in systems where water sits stagnant or is stored at temperatures that allow bacteria to multiply. In cooler months, water systems are less likely to reach those conditions. In summer, cold water pipes can warm up significantly, and properties that have been empty, or that have infrequently used outlets, carry a higher risk. Hot water systems that are not maintaining consistent temperatures add to that risk. This is why summer is consistently the period of highest concern, and why it is the most important time of year to check that your legionella risk assessment is current and reflects the property as it stands.

What a legionella risk assessment actually covers

A legionella risk assessment looks at the entire water system in a property: the tanks, cylinders, pipework, outlets, and any other points where water flows through or sits. A qualified assessor identifies where bacteria could grow, checks that hot and cold water temperatures are within safe ranges, looks for areas of stagnation such as dead legs or infrequently used taps, and reviews what controls are already in place. You receive a written report setting out what was found and what actions, if any, are needed. It is a practical document that tells you where you stand, not a pass or fail certificate.

How often does the assessment need to be done?

There is no single fixed rule that applies to every property. Current HSE guidance recommends that a legionella risk assessment is reviewed whenever there is reason to believe it may no longer be valid, and most assessors work to a two-year review cycle for typical residential and commercial properties. More complex systems, larger HMOs, or properties with cooling towers or spa pools may require more frequent review.

Simple domestic systems in single-occupancy lets are considered lower risk, but that does not mean they can be left without an assessment in place. A risk assessment needs to exist for all properties with a water system, even where the risk is assessed as low.

What triggers an out-of-cycle review?

A review is needed sooner than the next scheduled date if any of the following apply to your property:

• The property has been void for an extended period, or there is a change of tenancy

• Significant work has been carried out on the water system

• There has been a change in how the building is used

• A case of legionella has been reported in connection with the building

• There is any other reason to believe the current assessment is no longer valid

None of these are rare events in an active property portfolio. Building a review trigger into your management process means you are not relying solely on a calendar reminder.

Ready to get yours sorted?

If you are not sure when your last legionella risk assessment was carried out, or whether it still reflects your current water system, the best first step is a quick conversation. SE Asbestos Surveys carry out legionella risk assessments for residential and commercial properties across Essex, London and the South East. Call 07872054963 or get a quote online.