Legionella Risk Assessment Cost London — L8 Compliance Guide for Landlords

The Legal Requirement for Landlords

Landlords have a legal duty under the Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health (COSHH) Regulations 2002 to assess the risk from Legionella bacteria in their rental properties. The Health and Safety Executive (HSE) sets out how this must be done in its Approved Code of Practice L8 — Legionnaires' Disease: The Control of Legionella Bacteria in Water Systems.

Most residential letting properties are considered low risk, but the duty to assess still exists. For a typical single-occupancy rental flat or house, the risk assessment is straightforward and should be reviewed whenever there is a change in use or when the water system is altered. For HMOs, larger properties with stored hot water (calorifiers or vented cylinders), or properties with complex water systems, the risk is higher and the assessment more detailed.

What Does a Legionella Risk Assessment Cover?

A qualified assessor will inspect and document the following:

• Hot and cold water storage: Tank size, temperature, insulation, condition of float valves and overflow pipes
• Water temperature: Hot water should be stored at 60°C or above; cold water should be kept below 20°C. Temperatures are checked at outlets
• Dead legs and infrequently used outlets: Shower heads, garden taps, and any pipework that is rarely flushed are prime Legionella risk points
• Thermostatic mixing valves (TMVs): TMVs that blend hot and cold water can harbour bacteria if not correctly commissioned or maintained
• Showerheads and hoses: Flexible hoses and showerhead internals are inspected for scale buildup and biofilm
• Cold water storage tanks: Condition, lid security, insulation, and absence of debris

Legionella Risk Assessment Costs in London

For a standard single-occupancy residential rental property, expect to pay:

• Single flat (combi boiler, no stored water): £100-175
• House with vented cylinder or cold water tank: £150-250
• HMO with multiple bathrooms and stored water: £200-400
• Large HMO or block with calorifier: £350-600

Many London landlords combine the Legionella risk assessment with the annual Gas Safety Certificate inspection, which can reduce overall visit costs. Prestige Engineers can carry out the risk assessment alongside any gas or plumbing maintenance visit.

Low Risk Properties — What This Means

HSE guidance states that most residential properties served by a combination (combi) boiler — which heats water on demand with no storage — are inherently low risk. Where the risk is assessed as low, HSE does not require a written scheme of control, though documenting the assessment is still recommended. The risk assessment should be recorded in writing so that it can be produced to a local authority environmental health officer if required.

Low risk does not mean zero risk. Even with a combi boiler, infrequently used outlets such as a garden tap or a shower in a spare bathroom should be flushed regularly — weekly if unused for seven days or more.

Higher Risk Properties — Stored Water Systems

Properties with hot water cylinders (whether vented or unvented), cold water storage tanks in the loft, or calorifiers represent a higher risk category. For these properties a written scheme of control is recommended, setting out how temperature checks, outlet flushing, and periodic cleaning will be carried out. Annual inspection by a competent person is advised.

HMOs are particularly important because the water system serves multiple households, showers are used frequently, and the property may have periods of reduced occupancy during which water stagnates. HMO licensing conditions in many London boroughs now require evidence of Legionella risk management as part of the licence application.

Who Can Carry Out a Legionella Risk Assessment?

There is no specific statutory qualification for residential Legionella risk assessors, but assessors should have relevant training and understanding of HSE L8 and the associated Technical Guidance HSG274. Look for assessors who hold a Legionella risk assessment qualification from the Chartered Institute of Environmental Health (CIEH) or equivalent, and who carry professional indemnity insurance.

Prestige Engineers carries out Legionella risk assessments on residential and HMO properties across all 33 London boroughs, with written reports produced on the day of inspection.

How Often Should the Assessment Be Reviewed?

HSE guidance recommends reviewing the risk assessment whenever there is a reason to believe it is no longer valid — typically after a change of tenant, significant plumbing work, a change in occupancy pattern, or every two years as a minimum for higher-risk properties. For low-risk single-occupancy properties, a review at change of tenancy plus a brief annual check is considered adequate.