Legionella Risk Assessment: Legal Requirements for UK Landlords and Businesses

Legionnaires' disease is a potentially fatal form of pneumonia caused by Legionella bacteria. Property owners and employers have a legal duty to assess and control the risk.

What Is Legionella?

Legionella is a bacteria found naturally in water sources. It becomes dangerous when it grows in man-made water systems and is inhaled through water droplets (aerosols).

Conditions for Growth

Legionella thrives when:

• Water temperature is 20-45°C
• Water is stagnant (stored or recirculated)
• There is sediment, scale, or biofilm for nutrients
• Water systems have complex pipework with dead legs

Who Needs a Legionella Risk Assessment?

Employers

Under the Health and Safety at Work Act 1974 and Control of Substances Hazardous to Health (COSHH) Regulations, employers must assess risks from:

• Hot and cold water systems
• Cooling towers and evaporative condensers
• Spa pools and hot tubs
• Humidifiers and water features

Landlords

Landlords must assess legionella risk for:

• Residential rental properties
• Commercial premises
• Holiday lets
• HMOs (Houses in Multiple Occupation)

Duty Holders

Anyone in control of premises, including:

• Facilities managers
• Building owners
• Letting agents (if responsible)

Legal Framework

Key legislation includes:

| Legislation | Requirement | |-------------|-------------| | Health and Safety at Work Act 1974 | General duty to protect health | | COSHH Regulations 2002 | Assess and control hazardous substances | | Management Regulations 1999 | Risk assessment requirement | | Approved Code of Practice L8 (ACOP L8) | Practical guidance on compliance |

What Does a Legionella Assessment Cover?

1. Identify Potential Risks

• Water storage tanks (cold water storage cisterns)
• Hot water cylinders and calorifiers
• Pipework design (dead legs, little-used outlets)
• Shower heads and hoses
• Cooling systems
• Water features

2. Assess Who Is at Risk

• Employees
• Tenants and residents
• Visitors
• Vulnerable groups (elderly, immunocompromised)

3. Evaluate Controls

• Temperature monitoring
• System flushing
• Cleaning and disinfection
• Biocide treatment
• System design modifications

4. Record Findings

Document:

• The system assessed
• Risks identified
• Control measures in place
• Additional actions needed
• Review schedule

Temperature Control

The primary control method is temperature:

| Temperature | Effect on Legionella | |-------------|---------------------| | Below 20°C | Dormant (no growth) | | 20-45°C | Active growth zone | | 50°C | Killed in 2-3 hours | | 60°C | Killed in 32 minutes | | 70°C+ | Killed instantly |

Hot Water Requirements

• Store at 60°C minimum
• Distribute at 50°C+ at outlets
• Warning: Scalding risk - install TMVs (thermostatic mixer valves) where vulnerable people use outlets

Cold Water Requirements

• Store and distribute below 20°C

Control Measures

For Simple Systems (Domestic Properties)

• Set hot water cylinder to 60°C
• Run taps and showers weekly (especially in unused rooms)
• Clean shower heads quarterly
• Inspect cold water tanks annually
• Flush little-used outlets regularly

For Complex Systems (Commercial Buildings)

• Written scheme of control
• Temperature monitoring programme
• Regular system flushing
• Quarterly cleaning of shower heads
• Annual tank inspection and cleaning
• Biocide dosing (where appropriate)
• Monthly dip slide sampling
• Annual legionella testing

When to Use a Specialist

Consider professional assessment for:

• Large or complex buildings
• Cooling towers and evaporative condensers
• Healthcare premises
• Hotels and leisure centres
• Buildings with vulnerable occupants

Look for assessors who are:

• Members of the Legionella Control Association (LCA)
• Qualified to WMSoc or similar standards
• Experienced in your building type

Penalties for Non-Compliance

Failure to manage legionella risk can result in:

• Unlimited fines
• Imprisonment for individuals
• Enforcement notices
• Corporate manslaughter charges in fatal cases

Case Study

In 2023, a UK company was fined £1.8 million after a worker died from Legionnaires' disease contracted from a cooling tower. The company had failed to maintain adequate controls.

How Often to Review

Review your assessment:

• Annually as minimum
• When water systems change
• When building use changes
• After refurbishment or extension
• If legionella is detected
• After cases or outbreaks

Simple Landlord Checklist

For residential rental properties:

• [ ] Check hot water temperature (60°C at cylinder)
• [ ] Inspect cold water tank for debris
• [ ] Ensure tank has tight-fitting lid
• [ ] Run all taps and showers weekly
• [ ] Clean shower heads quarterly
• [ ] Flush system after void periods
• [ ] Record actions taken
• [ ] Review annually

Summary

Legionella risk assessments are a legal requirement, but for most properties, simple controls are sufficient. The key is maintaining appropriate temperatures and preventing water stagnation.

Next Steps

• Create a legionella risk assessment
• Read our COSHH assessment guide
• Learn about fire risk assessments