Legionella Risk Assessment in London: A Landlord's Legal Duty

Legionella Risk Assessment: What London Landlords Must Know

Legionella is a bacterium that thrives in water systems where temperatures sit between 20°C and 45°C and where stagnation or scale provide nutrients. In a residential property, the primary concern is Legionella pneumophila, the organism responsible for Legionnaires' disease — a potentially fatal form of pneumonia.

The Legal Framework

Three overlapping pieces of legislation govern landlord obligations in England:

• Health and Safety at Work etc. Act 1974 — imposes a general duty on employers and the self-employed to manage risks. Private landlords renting to tenants are considered to have duties akin to a person in control of premises.
• Control of Substances Hazardous to Health Regulations 2002 (COSHH) — Legionella is a biological agent classified as hazardous to health under COSHH. Regulation 7 requires assessment of the risk of exposure.
• Management of Health and Safety at Work Regulations 1999 — requires a suitable and sufficient risk assessment and implementation of controls.

The Health and Safety Executive's Approved Code of Practice L8 (Legionella: the control of legionella bacteria in water systems) and the associated Technical Guidance HSG274 provide the authoritative guidance on compliance. While an ACOP is not statute, failure to follow it means a landlord must demonstrate an equally effective alternative was used — in practice, this means following L8.

What the Assessment Must Cover

A residential Legionella risk assessment must identify:

• Whether water temperatures in the hot and cold systems can reach and sustain the bacterium's growth range
• Whether any part of the system is infrequently used, allowing water to stagnate
• Whether showerheads, hose connections, or spray taps create aerosols
• Whether the cold water storage tank (if present) is covered, clean, and insulated
• Whether the hot water cylinder achieves and stores water at 60°C
• The risk profile of the likely tenants (immunocompromised individuals, those over 45, smokers, and those with respiratory conditions face higher personal risk)

Higher-Risk Triggers in London Properties

Certain features common to London's housing stock elevate risk:

• Cold water storage tanks in loft spaces — extremely common in pre-1990 London properties before mains-pressure systems became standard. If uncovered, poorly insulated, or serving long pipework runs, stagnation and contamination are genuine risks.
• Combi boiler conversions with legacy pipework — when an old stored-water system is converted to a combi boiler, redundant pipework may remain connected and stagnant.
• HMOs with en-suite showers used infrequently — a room vacant between tenancies with a shower that sits idle for weeks is a risk point.
• Communal hot water systems in blocks — large calorifiers, recirculating hot water loops, and long dead-legs in apartment blocks require more rigorous assessment and typically annual inspections.

Documentation and Frequency

For a typical low-risk residential tenancy (mains-fed combi boiler, no storage tank, no immunocompromised tenant), a written assessment is still legally required but a basic document recording the assessment, the findings, and the control measures in place is sufficient. It does not require renewal on a fixed cycle but must be reviewed whenever there is a reason to suspect it is no longer valid — change of use, significant works, or a new high-risk tenant.

Failing to carry out any assessment exposes a landlord to enforcement action by the local authority environmental health team, unlimited fines, and civil liability if a tenant contracts Legionnaires' disease.