Many landlords are unaware they have a legal duty to assess and control the risk of Legionella bacteria in their rental properties. This requirement applies to all rental properties with water systems, from single lets to HMO portfolios. Failing to comply can result in serious penalties, and more importantly, can put your tenants' health at risk.
This guide explains everything you need to know about legionella risk assessments: what they are, why they matter, and how to comply with your legal obligations.
Key Points: Legionella Risk Assessment for Landlords
- Legal requirement: All landlords must assess and control legionella risks under the Health and Safety at Work Act 1974
- Applies to: Every rental property with a water system, regardless of property type
- Who can do it: Landlords can self-assess simple systems; complex systems need professional assessment
- Review frequency: Assess before letting, then review regularly (typically every 2 years) or when changes occur
- Cost: DIY assessment is free; professional assessments typically cost between 50 and 150 pounds
- Penalties: Unlimited fines and potential imprisonment for serious failures
What is legionella and why does it matter?
Legionella is a type of bacteria that can grow in water systems where conditions are favourable. The most serious species, Legionella pneumophila, causes Legionnaires' disease, a potentially fatal form of pneumonia. The bacteria spreads when people inhale tiny water droplets (aerosols) containing the bacteria, typically from showers, taps, or other water outlets.
Conditions that promote legionella growth
Legionella bacteria thrive in specific conditions:
- Water temperatures between 20°C and 45°C - The danger zone where bacteria multiply rapidly
- Stagnant water - In unused pipes, dead legs, or infrequently used outlets
- Scale, rust, and biofilm - Provide nutrients and protection for bacteria
- Storage tanks - Especially those without proper lids or insulation
In a typical rental property, the main risk areas are showers, mixer taps, hot water cylinders, and any sections of pipework that are rarely used.
Who is at risk?
While Legionnaires' disease can affect anyone, certain people are more vulnerable:
- People over 45 years old
- Smokers and heavy drinkers
- People with chronic respiratory conditions
- Those with weakened immune systems
As a landlord, you cannot always know the health status of your tenants, which is why controlling legionella risks is important for all rental properties.
Your legal duty: HSE guidance and ACOP L8
The Health and Safety at Work Act 1974
Under the Health and Safety at Work Act 1974, landlords have a duty to ensure, so far as is reasonably practicable, the health and safety of people affected by their work activities. Letting a property is considered a work activity, meaning you must take reasonable steps to protect tenants from foreseeable risks, including legionella.
ACOP L8: The Approved Code of Practice
The HSE's Approved Code of Practice L8 (Legionnaires' disease: The control of legionella bacteria in water systems) sets out how duty holders should comply with legionella requirements. While the ACOP itself has special legal status, the accompanying guidance document HSG274 Part 2 provides specific advice for landlords and other duty holders managing domestic hot and cold water systems.
ACOP L8 has special legal status. If you're prosecuted for failing to control legionella and you haven't followed the ACOP, a court will find you at fault unless you can show you complied in an equally effective way.
What the law requires
As a landlord, you must:
- Identify and assess the risk of legionella exposure in your property
- Implement controls to prevent or minimise the risk
- Keep records of your assessment and control measures
- Review the assessment regularly and when circumstances change
This applies to all rental properties with water systems, including:
- Single let houses and flats
- Houses in Multiple Occupation (HMOs)
- Bedsits and shared houses
- Properties let through agents
- Holiday lets and short-term rentals
What does a legionella risk assessment involve?
A legionella risk assessment examines your property's water system to identify conditions where bacteria could grow and spread. The assessment should be proportionate to the risk, meaning simple domestic systems require less detailed assessment than complex commercial installations.
Key areas the assessment covers
1. Water system identification
The assessor documents the water system layout, including:
- Type of water supply (mains, stored, or both)
- Hot water generation (combi boiler, cylinder, immersion heater)
- Cold water storage (if any)
- Distribution pipework and outlets
- Any unusual features or additions
2. Risk identification
The assessment identifies potential problem areas:
- Dead legs - Redundant or capped-off pipework where water can stagnate
- Infrequently used outlets - Taps or showers that may not be used regularly
- Cold water storage tanks - Especially those without proper lids, insulation, or maintenance
- Flexible hoses - Such as shower hoses, which can harbour bacteria
- Mixer valves and taps - Where hot and cold water combine
- Showerheads - Particularly if scaled or infrequently cleaned
3. Temperature assessment
Water temperature is critical for legionella control:
- Hot water storage should be at 60°C or above
- Hot water distribution should reach outlets at 50°C or above within one minute
- Cold water should remain below 20°C
4. Current control measures
The assessment reviews what controls are already in place and their effectiveness.
5. Recommendations
Based on findings, the assessment recommends appropriate control measures to reduce or eliminate risks.
When is a legionella risk assessment needed?
Before letting a property
You should carry out a legionella risk assessment before letting any property for the first time. This establishes a baseline understanding of the water system and any risks that need managing.
When the assessment should be reviewed
Review your legionella risk assessment:
- Regularly - The HSE recommends reviewing at least every two years for domestic properties
- After significant changes - Such as alterations to the water system, new pipework, or changes to how the property is used
- After a long void period - Before new tenants move in after the property has been empty
- If there are concerns - Such as tenant complaints about water quality or temperature
- Following any legionella-related incident - In the property or similar properties you manage
Void properties need attention. If a property is empty between tenancies, water can stagnate in the pipework, creating ideal conditions for legionella growth. Flush all outlets weekly during void periods, or thoroughly flush before new tenants move in.
Who can carry out a legionella risk assessment?
Self-assessment for simple systems
For most domestic rental properties with straightforward water systems, landlords can carry out the risk assessment themselves. A simple system typically means:
- Mains cold water supply (no cold water storage tank)
- Combi boiler providing instantaneous hot water
- Standard domestic pipework with no complex features
- No spa baths, water softeners, or other specialist equipment
The HSE provides guidance to help landlords conduct their own assessments. The key is understanding the water system, identifying risks, and implementing appropriate controls.
When professional assessment is advisable
Consider using a professional assessor for properties with:
- Cold water storage tanks - Particularly older properties with tanks in lofts
- Hot water cylinders with complex configurations
- Multiple bathrooms or numerous outlets
- Older or complicated pipework systems
- Shared water systems in HMOs - Higher risk due to multiple users
- Any features you don't fully understand
Professional assessors typically hold qualifications such as those from the Legionella Control Association (LCA) or City and Guilds accreditation in legionella risk assessment.
Cost considerations
DIY assessment
If you have a simple water system and feel confident assessing it yourself using HSE guidance, there is no cost beyond your time. Many landlords with combi boiler systems and straightforward pipework can complete a basic assessment in under an hour.
Professional assessment
Professional legionella risk assessments for domestic rental properties typically cost:
- Single let property: 50 to 100 pounds
- Larger property or HMO: 100 to 150 pounds
- Complex systems: May be higher depending on the work involved
Some assessors offer portfolio discounts for landlords with multiple properties.
Cost of control measures
Most control measures for domestic properties are low-cost or free:
- Flushing outlets regularly - Free
- Adjusting boiler temperature - Free
- Cleaning and descaling showerheads - Minimal cost
- Removing dead legs - One-off plumbing cost
- Tank inspection and maintenance - Variable depending on condition
Compared to the potential penalties and the cost of dealing with a legionella outbreak, compliance is highly cost-effective.
Practical control measures for landlords
Once you've identified the risks, you need to implement appropriate controls. For most domestic rental properties, the following measures are effective:
Temperature management
Hot water:
- Store hot water at 60°C or above in cylinders
- Ensure hot water reaches outlets at 50°C or above within one minute of running
- Set combi boilers to deliver water at an appropriate temperature
Cold water:
- Ensure cold water remains below 20°C
- Insulate cold water pipes in warm areas (such as airing cupboards) if necessary
- Ensure cold water tanks (if present) are properly insulated and covered
Scalding risk: Water at 60°C can cause scalding in seconds. If you have vulnerable tenants or the property includes a nursery or care setting, consider thermostatic mixing valves (TMVs) at outlets to deliver water at a safe temperature while maintaining higher temperatures in the system.
Flushing infrequently used outlets
Water should not stagnate in pipework. Advise tenants to:
- Run all taps and showers for at least two minutes weekly if not used regularly
- Flush the system after returning from holidays
During void periods, you (or your agent) should flush all outlets weekly.
Cleaning and maintenance
- Clean and descale showerheads at least quarterly, or more frequently in hard water areas
- Replace flexible shower hoses regularly, as they can harbour bacteria
- Inspect cold water tanks annually if present, checking for debris, corrosion, and proper covers
- Remove or cap dead legs where redundant pipework exists
Informing tenants
Provide tenants with basic information about:
- The importance of running infrequently used outlets
- Reporting any problems with water temperature or quality
- Not adjusting boiler or cylinder thermostats below recommended temperatures
A simple information sheet at the start of the tenancy is good practice.
Record keeping
You must keep written records of your legionella risk assessment and control measures. Records should include:
- The risk assessment itself - Including date, findings, and who conducted it
- Control measures implemented - What you've done to manage identified risks
- Monitoring records - Such as temperature checks if carried out
- Maintenance records - Cleaning, descaling, tank inspections
- Any incidents or concerns - And how they were addressed
Keep records for the duration of the tenancy and retain them for a reasonable period afterwards. These demonstrate compliance if you're ever challenged and help track when reviews are due.
Penalties for non-compliance
Legionella control is enforced by the HSE and local authorities. Failing to assess and control legionella risks can result in:
- Improvement notices requiring you to take action within a specified time
- Prohibition notices preventing use of the water system until it's made safe
- Prosecution with unlimited fines
- Imprisonment in cases of gross negligence, particularly if someone is harmed
If a tenant contracts Legionnaires' disease and your failure to assess and control risks contributed to their illness, you could face:
- Criminal prosecution under health and safety law
- Civil claims for compensation
- Significant reputational damage
Legionella compliance is not optional. While enforcement action against landlords is relatively rare, the consequences of getting it wrong can be devastating. A simple risk assessment and basic control measures protect both your tenants and yourself.
Getting started: A simple action plan
Step 1: Understand your water system
Know what type of boiler or water heater you have, whether there's any water storage, and the general layout of the pipework.
Step 2: Conduct or commission a risk assessment
For simple systems, use HSE guidance to assess the risks yourself. For complex systems, hire a professional.
Step 3: Implement control measures
Based on your assessment, put appropriate controls in place. Most domestic properties need only basic measures.
Step 4: Keep records
Document your assessment, controls, and any monitoring or maintenance.
Step 5: Review regularly
Reassess at least every two years, after changes, or following void periods.
Step 6: Inform tenants
Provide basic information about using the water system safely.
Frequently asked questions
Frequently Asked Questions
Yes. All rental properties require a legionella risk assessment, including those with combi boilers. However, properties with combi boilers and mains-fed cold water (no storage tanks) are generally lower risk, and landlords can often conduct the assessment themselves using HSE guidance. The assessment for such systems is straightforward and focuses on ensuring temperatures are correct and outlets are used regularly.
The HSE recommends reviewing your legionella risk assessment at least every two years for domestic rental properties. You should also review it after any significant changes to the water system, after a long void period, or if concerns arise about water quality or temperature. The assessment should be a living document that reflects the current state of the property.
For most domestic rental properties with simple water systems (combi boiler, mains-fed cold water, straightforward pipework), landlords can carry out the risk assessment themselves using HSE guidance. Professional assessment is advisable for properties with cold water storage tanks, complex pipework, multiple bathrooms, or shared water systems in HMOs. If you're unsure about any aspect of your water system, a professional assessment provides peace of mind.
Before new tenants move in after a void period, you should thoroughly flush all water outlets. Run all taps, showers, and any other water outlets for at least two minutes to clear stagnant water from the system. If the property will be empty for an extended period, arrange for weekly flushing, or ensure thorough flushing is done before re-letting. This prevents bacteria from multiplying in stagnant water.
Next steps
Legionella risk assessment is an important but often overlooked part of landlord compliance. The good news is that for most domestic properties, compliance is straightforward and low-cost.
Take action now:
- Review your property's water system and assess whether you can self-assess or need professional help
- Conduct or commission a risk assessment before your next tenancy starts
- Implement the recommended control measures
- Set up a system to review assessments regularly
For a complete overview of all your landlord compliance obligations, including gas safety, electrical safety, and fire safety, see our comprehensive Landlord Compliance Guide.
Check your compliance status - Use our free Landlord Compliance Checker to assess whether your property meets all the key legal requirements, including legionella, in just a few minutes.
Related resources:
- Landlord Compliance Guide - Complete overview of all landlord legal requirements
- Landlord Compliance Checker - Free tool to assess your property
- HSE Legionella Guidance for Landlords - Official HSE guidance