How Often Should a Legionella Risk Assessment Be Reviewed?

The short answer: review your legionella risk assessment at least every two years as a common industry benchmark — but certain events trigger an immediate review regardless of when the last one was done.

The longer answer depends on your building type, water system complexity, and whether anything has changed since the last assessment. Here is what ACoP L8 and HSG274 require.

What ACoP L8 says about review frequency

The 2013 edition of ACoP L8 removed the previous fixed two-year interval. Instead, it requires the risk assessment to be reviewed "regularly" and "whenever there is reason to suspect it is no longer valid."

In practice, every two years has become a common industry benchmark, though L8 itself requires review "whenever there is reason to suspect it is no longer valid." Most duty holders and assessors treat the two-year interval as a reasonable baseline for low-risk properties.

Events that trigger an immediate review

Regardless of when your last review was, you need a fresh assessment if any of these happen:

• Water system changes — new pipework, removed outlets, boiler replacement, additional water storage
• Building use changes — different occupant type, change from residential to commercial, new high-risk areas (showers added, spa installed)
• Extended building closure — any period where the building was unoccupied and water systems were stagnant (extended closures are a known risk factor for legionella growth in unused systems)
• Positive legionella sample — any detection of legionella bacteria triggers an immediate review and corrective action
• Near-miss or incident — any event suggesting the control measures are not working
• Refurbishment or construction — dust and debris can contaminate water systems
• Change of duty holder — new landlord, new building manager, change of responsible person

Review frequency by building type

Building type	Recommended review interval	Why
Simple residential let (single dwelling, combi boiler)	Every 2 years	Low complexity, low risk if well maintained
HMO or multi-let property	Every 2 years (annually if high turnover)	More outlets, more occupants, higher usage variation
Care home	Annually	Vulnerable occupants, higher regulatory scrutiny
Dental or GP practice	Annually	Dental units create aerosols, regulated healthcare environment
Hotel or B&B	Annually	Seasonal occupancy creates infrequently used outlets
School	Every 2 years (annually for boarding schools)	Holiday closures create stagnation risk
Office or commercial building	Every 2 years	Standard risk unless complex water systems

These intervals are the maximum gap between reviews. Any trigger event requires an immediate review regardless.

What "reviewing" actually means

A review is not just re-reading the previous document. A proper review involves:

1. Physical inspection — walk the building and check every outlet, tank, and pipe run against the previous assessment
2. Temperature checks — verify that stored and delivered water temperatures still meet thresholds (hot water stored at 60°C or above, delivered at 50°C or above at outlets, cold water below 20°C)
3. System changes — identify any new pipework, removed outlets, or changes since the last assessment
4. Occupancy changes — note any difference in building use or occupant type
5. Control measure effectiveness — are the existing controls still working? Are temperature logs showing consistent compliance?
6. Update the risk assessment document — amend and re-sign with the new review date

If you carry out your own assessment on a simple domestic property, this process can take 30-60 minutes per property. Complex buildings typically require a specialist assessor.

The cost of getting it wrong

HSE inspectors will check:

• That a written risk assessment exists
• That it has been reviewed within a reasonable timeframe
• That review dates match trigger events (if the building was refurbished and the assessment predates the work, that is a problem)

Enforcement ranges from improvement notices (fix it within a specified timeframe) to criminal prosecution under health and safety legislation.

How to track review dates

For a single property, a calendar reminder works. For multiple properties, review dates quickly become hard to track — especially when trigger events create ad hoc reviews outside the normal cycle.

LegioLog's Risk Assessment Template Generator creates a building-type-specific template that includes a review-date field so your next review date is documented from the start.

For the full regulatory background, see our guide to ACoP L8 and HSG274.

This guide covers legionella risk assessment review requirements under ACoP L8 for England, Wales, and Scotland. This is general compliance guidance, not legal or professional advice — for site-specific advice, consult a competent person.

Sources

• HSE — ACoP L8: Legionnaires' disease
• HSE — Identify and assess sources of risk
• HSE — Legionella and landlords' responsibilities