Legionella Risk Assessment for Landlords

A legionella risk assessment looks at the water systems in a rented property, hot and cold, to identify conditions that could allow legionella bacteria to grow and, in rare cases, cause Legionnaires' disease. Unlike a gas safety certificate or an EICR, there is no single legal document called a "legionella certificate" that you renew on a fixed schedule. Instead, landlords have an ongoing duty to assess and manage the risk, and to keep evidence that they have done so.

For most standard domestic lettings, this is a manageable, low-cost task rather than something that requires an expensive specialist survey. The detail that matters is understanding when a simple, landlord-completed assessment is enough, and when a property's water system is complex enough to justify bringing in a professional.

Legal basis

The duty comes from general health and safety law rather than a legionella-specific regulation aimed at landlords. The Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 (COSHH) place a duty on anyone who controls premises, including landlords of rented residential property, to assess and control risks from hazardous substances, which includes legionella bacteria in water systems. The Health and Safety Executive's Approved Code of Practice (L8) and its more detailed guidance (HSG274) set out how to carry out and document a suitable assessment.

In practice, this means every landlord has a duty to think about legionella risk in their rented properties, but the level of formality expected scales with the complexity of the water system, not a fixed one-size-fits-all checklist. A simple house with a combi boiler and no water storage tank presents a genuinely different risk profile to a large HMO with a cold water storage tank feeding several bathrooms, and the assessment should reflect that difference.

This is a duty of control and management rather than a duty to produce a specific certificate, which is why it is easy for landlords to overlook. There is no equivalent of a Gas Safe engineer's stamp of approval to point to, so the responsibility sits with the landlord to show a reasonable, documented process was followed, using HSE's published guidance as the reference standard.

DIY versus professional assessment

For most single-let domestic properties with a straightforward mains-fed system, such as a combi boiler with no cold water storage tank and no unusual pipework, a landlord can carry out their own risk assessment using HSE guidance without hiring a specialist. This typically involves checking the system for stored or standing water, identifying any redundant pipework or infrequently used outlets, confirming the water heater is set to an appropriate temperature, and documenting what you checked and when.

A professional assessment becomes more worthwhile once a property has features that increase risk or complexity: a cold water storage tank in the loft, a large or unusually configured pipe system, communal water systems shared across several units such as in an HMO or converted block, or any part of the system that is used infrequently, such as an outside tap or a rarely used shower in a spare bathroom. A specialist can also help if you are unsure how to interpret HSE guidance for your specific property, or if you manage several properties and want a consistent, defensible process across all of them.

Cost for a professional legionella risk assessment varies with property size and system complexity, and by whether ongoing monitoring, such as periodic temperature checks or tank inspections, is included as well as the initial assessment. A single straightforward HMO assessment costs noticeably less than an ongoing monitoring contract across a portfolio of shared properties, so get a clear scope from any specialist before committing, and ask whether the quote covers a one-off assessment or an ongoing service.

Review frequency

There is no fixed statutory renewal interval for a legionella risk assessment in the way there is for a gas safety certificate or an EICR. HSE guidance recommends reviewing the assessment periodically, commonly cited as every two years for straightforward properties, and sooner if something changes that could affect the risk. Triggers for an earlier review include a change of tenant, a void period where the property has been unoccupied and water has been standing in the system, any alteration to the plumbing or heating system, or a report of a problem such as unusually low water temperature from the hot water system.

Document each review, even if the outcome is simply "no significant change, no action required." A dated record showing you have thought about the risk periodically is what demonstrates compliance if it is ever questioned, rather than the specific format of the document itself.

Landlords who manage a small portfolio often find it easiest to review legionella risk at the same time as an annual gas safety visit or a routine property inspection, rather than treating it as a separate task on its own calendar. Bundling it with a visit you are already making saves time and reduces the chance that the review gets forgotten entirely in a busy year.

Simple properties versus complex systems

A single let house or flat with a combi boiler, no water tank, and normal day-to-day water use by the tenant is about as low risk as domestic lettings get, since there is little standing water and the system is used regularly enough to prevent stagnation. For this type of property, a landlord-completed assessment, reviewed roughly every two years or after a change of tenant, is usually a proportionate response.

Risk increases with any of the following: a cold water storage tank, particularly one with a loose or missing lid; pipework that serves fittings which are rarely used, such as an outdoor tap, a garage sink or a guest bathroom; shared water systems across multiple units, as in an HMO or a block of flats with a communal supply; and extended void periods where water sits unused in the system for weeks at a time. For a shared house or HMO where several of these risk factors combine, it is worth pairing a legionella assessment with your other HMO compliance checks, since a licensing inspection may also ask about water safety measures. See our landlord certificates checklist for how this fits alongside your other compliance documents, and our landlord legal responsibilities guide for the wider set of duties that apply to any rented property regardless of type.

A practical habit that reduces risk in any property, simple or complex, is running taps and showers for a few minutes at the start of a new tenancy or after any void period, which flushes out water that has been sitting in the pipes. This costs nothing and addresses one of the most common risk factors directly.

How Property HQ helps

Property HQ gives you a place to log your legionella risk assessment date, the outcome, and when it is next due for review, alongside your other compliance certificates for the same property. That keeps a low-frequency, easy-to-forget task visible in the same place as your annual gas safety and five-yearly EICR renewals, rather than relying on a separate note or folder that is easy to lose track of.

Disclaimer

This guide is general information for UK landlords, not health and safety advice. Check current HSE guidance (L8 and HSG274) for the detail relevant to your property, and use a qualified specialist for complex or communal water systems.