Legionella Risk Assessment for Landlords: Is It Mandatory? (2026 UK Guide)

Legionella is one of the least understood parts of landlord compliance. Some landlords are told they must pay for expensive testing every year, while others have never heard of it. The truth sits in the middle: there is a clear legal duty, but for most homes it can be met with a simple assessment and a few sensible precautions.

This guide explains exactly what the law requires, how to carry out a legionella risk assessment, and when it is worth bringing in a professional.

What is Legionella and Legionnaires’ disease?

Legionella bacteria are found naturally in water. In the right conditions they can multiply in man-made water systems, such as hot and cold water pipes, tanks and showers.

People can catch Legionnaires’ disease, a potentially fatal form of pneumonia, by breathing in tiny droplets of contaminated water, for example from a shower. It is not spread from person to person, and drinking contaminated water does not usually cause it.

When does Legionella become a risk?

• Water is held between 20°C and 45°C, the temperature range where bacteria grow fastest
• Water is stored or stagnant, for example in tanks, unused pipes or empty properties
• There is scale, rust, sludge or biofilm in the system, which bacteria can feed on
• Water is turned into droplets, mainly by showers and spray taps
• Occupants are more vulnerable, such as older people, smokers and people with weakened immune systems

Is a legionella risk assessment mandatory for landlords?

Yes, landlords must assess the risk. Under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 (COSHH), anyone who lets a property has a duty to make sure tenants are not exposed to health risks, including Legionella. The Health and Safety Executive’s guidance, the Approved Code of Practice L8 and HSG274, explains how to meet that duty.

Can landlords do their own legionella risk assessment?

Yes. For most simple homes, a landlord who understands the risks can carry out the assessment themselves. The HSE says the assessment does not need to be complicated or expensive. However, if you are not confident, or the property has a more complex water system, you should use a competent professional.

What does a legionella risk assessment cover?

A legionella risk assessment looks at the whole water system and asks four questions:

1. Where could bacteria grow? For example, hot water cylinders, cold water tanks, unused pipes (“dead legs”) and showers.
2. Who could be exposed? The tenants, and whether any are more vulnerable.
3. How likely is exposure? Based on water temperatures, how often outlets are used and the condition of the system.
4. What controls are needed? Practical steps to keep the risk low, and who is responsible for them.

The result should be a short written record of what you found, the controls in place and any actions needed.

Legionella risk assessment checklist for landlords

Use this checklist as a starting point for a simple residential property. Record your answers, the date and any actions taken.

If all the answers are positive and the property has a combi boiler with no stored water, the risk is usually low and simple controls are enough.

How to record your assessment

Write down the date, the property address, who carried out the assessment, the type of water system, the temperatures you measured and the controls you have put in place. Note any actions, such as removing a dead leg or replacing a tank lid, and the date each one was completed. Keep the record with your other compliance documents and share a copy with your letting agent if they manage the property. A dated record like this is exactly what an inspector would expect to see.

Simple control measures for rental properties

• Keep hot water hot: set hot water cylinders to store water at 60°C.
• Keep cold water cold: insulate cold water pipes and tanks, especially near heat sources.
• Avoid stagnant water: remove dead legs and flush little-used outlets.
• Keep tanks covered and clean: cold water tanks should have a secure lid and be checked for debris.
• Clean showers: descale and disinfect shower heads regularly, or ask tenants to.
• Flush after void periods: run all taps and showers for several minutes before a new tenant moves in.

What to tell your tenants

Tenants play an important part in controlling Legionella. Give them simple written advice to:

• Run taps and showers that are not used often, especially after holidays
• Keep shower heads clean and free from limescale
• Not adjust the hot water cylinder temperature below the recommended setting
• Tell you straight away if the hot water is not heating properly or the cold water runs warm

When should landlords use a professional?

A professional legionella risk assessment is a good idea when:

• The property has a cold water storage tank or a large hot water cylinder
• It is an HMO or a block of flats with shared water systems
• There are vulnerable tenants, such as elderly residents
• The property has been empty for a long time or the system has been altered
• Your letting agent, insurer or licensing scheme asks for a professional report
• You are simply not confident assessing the system yourself

A professional assessor will inspect the system, take temperature readings, check tanks and pipework, and give you a written report with clear actions. This gives you strong evidence that you have met your legal duty.

How often should a legionella risk assessment be reviewed?

The HSE does not set a fixed date for reviewing a legionella risk assessment. Instead, you should review it whenever there is reason to think it may no longer be valid, such as:

• Changes to the water system, such as a new boiler or tank
• A change of tenant, especially if new tenants are more vulnerable
• The property being empty for an extended period
• A case of Legionnaires’ disease linked to the property

Many landlords and letting agents choose to review the assessment every one to two years as good practice, and at each change of tenancy.

Legionella in HMOs and blocks of flats

HMOs and blocks often have larger, more complex water systems with storage tanks and longer pipe runs, and more people using the same supply. That means a higher risk, and more need for regular checks. In these buildings, landlords and managing agents typically:

• Use a professional risk assessment and keep a written scheme of control
• Check water temperatures at key outlets on a regular schedule
• Inspect cold water tanks at least once a year
• Keep a log of all checks, flushing and maintenance

Legionella is one of several compliance areas for HMOs. Our landlord certificates checklist covers the others.

What happens if landlords ignore Legionella?

Failing to assess and control the risk of Legionella is a breach of health and safety law. If a tenant becomes ill, the landlord could face investigation and prosecution by the HSE or the local council, with unlimited fines and, in the most serious cases, imprisonment. Civil claims from affected tenants are also possible.

A written assessment and a record of the controls you have put in place are your best protection.

How much does a legionella risk assessment cost?

Doing the assessment yourself costs nothing but your time. A professional assessment usually costs more for larger or more complex buildings. At Landlord Sure, legionella risk assessments start from £200 for rental properties in London, including a written report with clear recommendations.

You can book a legionella risk assessment alongside other checks such as a gas safety certificate, EICR or fire risk assessment.

Frequently asked questions

Sources: HSE – Legionella: landlords’ responsibilities; HSE – Approved Code of Practice L8; NRLA – Legionella for landlords. Information checked October 2026. This guide is general information, not legal advice.