Legionella Risk Assessment: What London Landlords Must Do
Legionella risk assessments are often misunderstood by London landlords. Here is what the HSE requires, what the assessment covers and when you need a specialist to carry it out.
Legionella is a bacterium that thrives in water systems at temperatures between 20°C and 45°C. When inhaled as fine water droplets — from a shower, spray tap or cooling tower — it can cause Legionnaires' disease, a potentially fatal form of pneumonia. London landlords have a legal duty under the Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 to manage the risk of Legionella in their rental properties.
Is a Legionella risk assessment a legal requirement for landlords?
The HSE's guidance ACoP L8 and HSG274 require landlords to assess and control the risk of Legionella in all rental properties. While a formal assessment is not listed as a statutory certificate in the same way as a gas safety certificate, the duty to carry out a risk assessment is underpinned by primary legislation. The HSE can prosecute landlords who fail to take appropriate steps to manage Legionella risk.
For most domestic rental properties with a standard mains-fed plumbing system and a conventional boiler, the risk is low — but a written assessment demonstrating that the landlord has considered the risk is still required.
What does a Legionella risk assessment cover?
A residential Legionella risk assessment for a rental property examines:
- Hot and cold water system design and configuration
- Water storage (cold water storage tanks, unvented cylinders)
- Hot water temperatures throughout the system
- Cold water temperatures at outlets
- Dead legs — sections of pipework where water sits without circulating
- Infrequently used outlets where water can stagnate
- Shower heads and spray fittings
- Any scale, corrosion or biofilm visible in accessible pipework
When is the Legionella risk highest?
Domestic Legionella risk is highest in properties with:
- Cold water storage tanks (common in properties with older plumbing or combination boilers feeding a tank)
- Hot water cylinders operating below 60°C
- Infrequently used water outlets (spare rooms, holiday lets)
- Dead legs from previous plumbing modifications
- Properties that have been empty for extended periods before letting
What are the control measures?
For low-risk domestic properties, the primary controls are straightforward: ensure hot water is stored at or above 60°C and delivered at or above 50°C, flush infrequently used outlets regularly, and descale shower heads and taps periodically. Where risk is higher — larger properties, cold water storage tanks, complex systems — more formal management is required.
How often should the assessment be repeated?
The HSE recommends reviewing the risk assessment when there is reason to believe it may no longer be valid — typically when a new tenancy starts, when significant plumbing work is carried out, or if a tenant reports a concern. For most domestic lets, reviewing the assessment at each tenancy change is sufficient.
Frequently asked questions
Does every London landlord need a Legionella risk assessment?
Yes — all landlords have a duty to assess Legionella risk under HSE guidance, regardless of property type. For standard domestic properties with mains-fed plumbing, the risk is typically low but must be documented.
How much does a Legionella risk assessment cost?
For a standard domestic rental property, a Legionella risk assessment typically costs £80–£150. It can often be combined with a gas safety or EICR visit to reduce costs.
Can a landlord do their own Legionella risk assessment?
For simple domestic properties, the HSE guidance states that landlords can carry out the assessment themselves if they are competent to do so. However, a professional assessment provides a documented record that the duty has been met.
What temperature should hot water be stored at to prevent Legionella?
Hot water should be stored at 60°C or above and delivered at 50°C or above within one minute of running. Cold water should be stored and supplied below 20°C.