Legionella in Rental Properties — A London Landlord's Practical Guide
Legionella bacteria can grow in water systems and cause Legionnaires disease. This guide explains a landlord's duty to conduct risk assessments, what properties need checking, and what simple controls prevent legionella growth.
Legionella and Landlord Obligations
Legionella bacteria cause Legionnaires' disease — a potentially fatal form of pneumonia. The bacteria grow in water systems where water temperatures are between 20-45°C and where there is a source of nutrients (scale, biofilm, rust). Legionella can be released as an aerosol from showers, spray taps and other water outlets, where it can be inhaled.
Under the Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health (COSHH) Regulations 2002, landlords have a duty to manage legionella risk in their rental properties.
Who Needs a Formal Risk Assessment?
The Health and Safety Executive (HSE) guidance (L8, ACOP) distinguishes between different property types:
- Simple domestic properties (single let): A formal written risk assessment is required, but in practice for a simple property with a single household, mains-fed hot and cold supply, and a combi boiler, the risk is very low. The HSE acknowledges this and landlords can carry out and record their own basic risk assessment.
- HMOs: Greater risk due to multiple occupants, potential for infrequent use of outlets (guest bathrooms, showers not used regularly), and more complex water systems. A professional legionella risk assessment is strongly recommended.
- Properties with hot water storage cylinders: Unvented or vented cylinders that store hot water at 45-60°C require careful temperature management. Water must be stored at minimum 60°C and delivered at no more than 50°C at outlets (with thermostatic mixing valves).
- Properties with cooling towers, spa pools or decorative water features: Highest risk; mandatory formal risk assessment and control scheme required.
Simple Control Measures for Rental Properties
For most standard London rental properties, legionella risk is controlled by:
- Hot water storage at 60°C: Cylinder thermostats set to 60°C kill legionella. Check and set at every annual service.
- Cold water below 20°C: Keep cold water pipes away from heat sources; lag pipes in warm areas (boiler cupboard, loft in summer).
- Flush infrequently used outlets: Run taps, showers and outlets for 2 minutes if a property has been unoccupied for a week or more before new tenants move in.
- Descale showerheads: Showerhead descaling removes biofilm that harbours legionella. Landlords should descale and disinfect showerheads between tenancies.
- Avoid dead legs: Pipework runs that terminate without flow (capped-off pipes, old appliance connections) harbour stagnant water. Remove or flush regularly.
Legionella Risk Assessment Cost in London
Professional legionella risk assessments for London residential properties:
- Single let property: £80-150
- Small HMO (3-5 persons): £150-250
- Large HMO or block of flats: £300-600
Frequently asked questions
Do all landlords need a legionella risk assessment?
All landlords must manage legionella risk, but for simple single-let properties with a combi boiler and mains-fed cold water, the risk is very low and landlords can carry out and record their own basic assessment. HMOs and properties with hot water storage cylinders should have a professional assessment.
How often should a legionella risk assessment be reviewed?
The HSE recommends reviewing the risk assessment regularly and whenever anything changes that could affect the risk — such as new pipework, changes in water usage patterns, a new type of outlet fitted, or if the property is unoccupied for a period. For most residential properties, an annual review is appropriate.
What temperature should a hot water cylinder be set to?
A minimum of 60°C to kill legionella bacteria. Water at 60°C is hot enough to cause scalding, so thermostatic mixing valves (TMVs) at outlets deliver water at a safe 48-50°C while the stored water remains at lethal-to-legionella temperature.
Is legionella in rental properties common in London?
Legionella cases from domestic rental properties are rare in London. The main risk factors are: hot water stored at too low a temperature (45-50°C range is ideal for legionella growth), long periods of building vacancy creating stagnant water, and complex HMO water systems with multiple tenants using water irregularly.