Landlord guide

Reviewed 18 August 2026

How often should a landlord Legionella risk assessment be reviewed?

This is where most landlord Legionella advice goes wrong. A conventional review interval gets repeated often enough that it starts to be described as law, and landlords end up believing an assessment "expires".

The guidance below separates what is required, what is conventional and what actually changes the risk in a rental property.

The short answer

There is no prescribed statutory frequency for reviewing a domestic landlord's Legionella risk assessment. The requirement is to review it periodically, and to review it whenever there is reason to think it is no longer valid.

In practice that means two things running together: a sensible periodic check, and a list of events that trigger a review regardless of when the last one was.

The widely repeated claim that the law requires a new assessment every one or two years is not correct for residential lettings. Two years is a common convention, not a statutory deadline.

General information, not legal advice. This guide describes the position in Great Britain. Northern Ireland is regulated by HSENI, and the Republic of Ireland has a separate legal framework — see the country pages.

What the guidance actually says

The HSE's position for landlords is that the assessment should be reviewed periodically, and specifically whenever there is reason to believe the original assessment is no longer valid. No fixed number of months or years is prescribed for domestic lettings.

That is a deliberate choice. A flat with a combi boiler occupied continuously by the same tenant for four years has barely changed. A short-let with a stored cylinder that sits empty for weeks changes constantly. One review interval cannot be right for both.

Correcting the "every two years by law" misconception

Two years is a frequently used convention for simple domestic properties, and reviewing on that sort of cadence is perfectly sensible. It is not a legal deadline, an expiry date or a renewal requirement, and an assessment does not become invalid the day after the interval passes.

You will see one-year and two-year intervals presented as legal requirements in marketing material and even in some letting-agent checklists. Treat any source that states a statutory renewal period for domestic lettings with caution, and check it against the HSE pages linked at the foot of this guide.

Events that should trigger a review

Work on the plumbing, hot-water system, cylinder, tank or shower
A change from a stored system to instantaneous hot water, or the reverse
The property standing empty for a period, or a long unoccupied wing or room coming back into use
A change of tenancy, or a material change in how the property is occupied
New occupants who may be more susceptible to infection
Outlets falling out of use, or new outlets being added
A tenant reporting discoloured water, poor hot-water temperature or a persistent problem
A case of Legionnaires' disease associated with the property
Anything that makes you doubt the original assessment still describes the property

Periodic review versus reassessment

Periodic review: A check that the existing assessment still describes the property and that controls and actions are being carried out. Often short, and may end with "no change".
Triggered review: Prompted by an event on the list above. Focused on what changed and whether it alters the findings.
Full reassessment: Warranted when the system itself has changed materially, when the property has been substantially altered, or when the earlier record is no longer a fair description.

How LegionellaWise handles review dates

You choose a review date and LegionellaWise reminds you at 30 days, 7 days and on the day. That reminder is a prompt for your own diary. It is not a statutory expiry date, and the report does not become invalid when it passes.

Because each report is versioned, a review that changes nothing still leaves a dated record showing you looked. A review that does change something produces a new version with the previous one preserved, so the history of the property stays intact.

Questions landlords also ask

Is a Legionella risk assessment valid for two years?

Validity is not time-limited by statute for residential lettings. An assessment remains valid for as long as it accurately describes the property and its risks, which is why event-based triggers matter more than the calendar.

Does the assessment expire when the reminder date passes?

No. A reminder date is one you chose as a prompt to look again. Nothing about the record changes when it passes.

Do I need a new assessment at every change of tenant?

Not automatically. A changeover is a good moment to confirm the assessment still describes the property, deal with any stagnation from the void and pass water-use information to the new tenant.

How often should temperatures be checked between reviews?

For a simple domestic property there is no prescribed monitoring frequency, and the routines used in healthcare or large commercial buildings should not simply be transplanted. Let the risk assessment decide what, if anything, needs periodic checking.

See whether guided self-assessment fits your property

The free suitability check asks a short set of questions about the water system, the building and the occupants, then tells you plainly whether guided self-assessment looks appropriate or whether the property should go to a specialist.

Check if my property is suitable See how LegionellaWise works

Official sources

General information, not legal advice. Requirements and guidance differ between jurisdictions — check the country page that applies to your property.