Independent UK guide
Legionella risk assessment: who needs one and how to do it
If you are an employer, or you control a building, or you rent out a home, you have a legal duty to assess the risk from legionella in the water system. For most small rental properties that assessment is simple, and HSE says most landlords can do it themselves.
Last reviewed October 2026 against HSE guidance.
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What a legionella risk assessment is
A legionella risk assessment is a check of a building's hot and cold water system. It looks for the conditions that let legionella bacteria grow and spread, decides whether anyone could be exposed, and sets out what you will do to keep the risk low.
Legionella bacteria cause Legionnaires' disease, a serious form of pneumonia. People catch it by breathing in small droplets of contaminated water, for example from a shower. HSE lists the conditions that raise the risk:
- water in all or part of the system sitting between 20°C and 45°C
- water that is stored or recirculated
- outlets that create breathable droplets, such as showers and spray taps
- rust, sludge, scale or biofilm that feed the bacteria
The assessment is the first of five duties HSE sets out. You must identify and assess sources of risk, manage them, prevent or control them, keep the right records, and carry out any other duties that apply to you.
Who needs one
| Who you are | What applies to you | Read next |
|---|---|---|
| Landlord of a house, flat or room | A duty to assess the risk. It does not need to be an in-depth assessment and you can usually do it yourself. | Landlord guide |
| Letting or managing agent | The same duty, where the agreement gives you control of the property or its water system. | Landlord guide |
| Employer or business with premises | A duty to assess, control and keep records. Recording the findings is a statutory duty if you have 5 or more employees. | Legal requirements |
| Care home, healthcare, hotel, leisure | The same duties, with more people at higher risk and more complex systems. Most use a specialist assessor. | Assessment costs |
| Private landlord in Scotland | Assess before the property is first let and review at least every two years. | Scotland |
What the assessment covers
A simple assessment walks through the water system from where water enters the building to every outlet. For each part it asks whether water could stagnate, sit at a temperature that suits legionella, or reach someone as a spray.
- The system. Mains-fed or stored water, a combi boiler or a hot water cylinder, any cold water tank, and the pipework layout.
- Temperatures. Hot water stored at 60°C or above and reaching 50°C at outlets within a minute. Cold water below 20°C. See legionella temperatures.
- Stagnation. Dead legs, unused outlets, and any period when the property stands empty.
- Outlets that spray. Showers, spray taps and anything else that makes fine droplets.
- Who is at risk. Older people, smokers and people with existing illness are more likely to become seriously ill.
- Controls and review. What you will do, who will do it, and when you will look again.
Our free template sets these out as a form you can fill in during a walk round the property.
Do it yourself or use a professional?
HSE's guidance for landlords is direct: “Most landlords can assess the risk themselves and do not need to be professionally trained or accredited.” It adds that anyone who does not feel competent, or does not want to, can arrange for someone else to do it.
| Situation | Sensible route |
|---|---|
| Single let with a combi boiler, no stored water, used every day | Do it yourself with a template. HSE describes this kind of system as a typical low-risk example. |
| Property with a cold water tank or hot water cylinder | Still within reach of most landlords. Check tank condition and stored temperatures carefully. |
| HMO, block of flats with shared systems, or a property often left empty | Consider a professional. Systems are larger and stagnation is more likely. |
| Business premises, care home, hotel, school | Use a competent assessor. You also need a written scheme and records. |
For typical prices see what a legionella risk assessment costs.
Common myths
- “You need a legionella certificate.” HSE says health and safety law does not require landlords to obtain or produce a ‘legionella test certificate’. More on certificates.
- “It must be redone every year.” In England, Wales and Northern Ireland the law sets no fixed interval. You review it periodically and when something changes. How often to review.
- “You have to test the water.” HSE says testing is not usually required for domestic hot and cold water systems. When testing is needed.
- “Only a qualified assessor can do it.” The law asks for a competent person. For a simple domestic system that can be the landlord.
Questions people ask
Is a legionella risk assessment a legal requirement?
Yes, there is a legal duty to assess the risk if you are an employer, control premises or rent out a property. The duty comes from the Health and Safety at Work etc Act 1974 and the COSHH Regulations. The law does not say the assessment must be done by a professional or produce a certificate.
Can I do my own legionella risk assessment?
For a simple domestic rental, usually yes. HSE says most landlords can assess the risk themselves and do not need to be professionally trained or accredited. Larger or more complex systems are better assessed by a specialist.
How long does a legionella risk assessment take?
A walk round a small rental with a combi boiler takes well under an hour. Properties with stored water tanks, several bathrooms or shared systems take longer because there are more temperatures and outlets to check.
How much does a legionella risk assessment cost?
Published UK prices for a domestic rental property are roughly £70 to £200. Commercial premises usually start at £200 to £500 and rise with the size of the system. Doing it yourself with a template costs nothing but your time.
Sources
- HSE: Legionnaires' disease, what you must do
- HSE: Legionella and landlords' responsibilities
- HSE: What Legionnaires' disease is and typical symptoms
- HSE: Hot and cold water systems
- HSE: Approved Code of Practice L8, The control of legionella bacteria in water systems
- Scottish Government: Repairing Standard statutory guidance for private landlords, Annex D
Checked against these sources in October 2026. This page is general information, not legal advice.
Start with the free template
An editable Word template for a simple rental property, based on the points HSE asks landlords to consider.
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