How Often Do You Need a Legionella Risk Assessment?

08.04.26 05:35 PM - By Darragh

It's one of the most common questions we get asked: 'How often do I need to redo my Legionella risk assessment?' The short answer is that there's no single fixed interval mandated by law — but the practical answer is more nuanced.

HSE's Approved Code of Practice L8 states that risk assessments should be 'regularly reviewed' and updated whenever there's reason to believe the assessment may no longer be valid. The generally accepted industry standard — and the recommendation of the Legionella Control Association (LCA) — is that risk assessments should be reviewed at least every two years.

There are several triggers that mean your risk assessment should be reviewed or redone before the two-year mark:

Changes to the water system — new pipework, a new tank, additional outlets, or system modifications

Changes to building use — a new tenant, a change from office to residential, or a change in occupancy patterns

A Legionella positive result — any confirmed Legionella detection should trigger a review

A Legionella positive result — any confirmed Legionella detection should trigger a review

An outbreak or notifiable case associated with the building

An outbreak or notifiable case associated with the building

Significant changes to water supply or treatment

Significant changes to water supply or treatment

Recommendations from the previous assessment that haven't been implemented

Recommendations from the previous assessment that haven't been implemented

New HSE guidance or changes to legislation

For most residential and commercial buildings, we recommend a full risk assessment review every two years, with ongoing monitoring (temperature checks and sampling) in between. For healthcare and high-risk settings, annual reviews are often appropriate. And whenever you make changes to your water system, get the assessment updated — even if it was only done six months ago.

For most residential and commercial buildings, we recommend a full risk assessment review every two years, with ongoing monitoring (temperature checks and sampling) in between. For healthcare and high-risk settings, annual reviews are often appropriate. And whenever you make changes to your water system, get the assessment updated — even if it was only done six months ago.

Remember: a risk assessment isn't a one-and-done document. It's a living record of your water system's risks and controls. If the building changes but the assessment doesn't, it becomes worthless — and potentially a liability.

Remember: a risk assessment isn't a one-and-done document. It's a living record of your water system's risks and controls. If the building changes but the assessment doesn't, it becomes worthless — and potentially a liability.

Not sure when your last assessment was? Get in touch for a free compliance check.

Darragh