Legionella Risk Assessment —
What Landlords Must Do

What is the legal obligation?

Every landlord in England and Wales has a legal duty to assess the risk from exposure to Legionella bacteria for their tenants. This obligation applies to all residential rental properties regardless of whether they have gas, how old the property is, or how recently it was let.

The HSE explicitly states that for simple residential properties — a house or flat with a conventional combi boiler or cold water storage tank and normal hot and cold water outlets — a landlord can conduct a straightforward self-assessment. What is not optional is doing it at all, recording it, and reviewing it periodically.

What is Legionella?

Legionella bacteria occur naturally in water. At low levels and in cold or very hot water they present minimal risk. The bacteria multiply and become dangerous when water is stored or circulated at temperatures between 20°C and 45°C — the warm stagnant conditions that can occur in poorly maintained water systems.

Legionnaires' disease is a serious form of pneumonia caused by inhaling water droplets containing Legionella. It is not transmitted person to person. The risk in a typical well-maintained domestic property is low — but the legal duty to assess and control it still applies.

What the risk assessment must cover

• Water system type — combi boiler with no storage tank carries very low risk; a cold water storage tank in a loft requires closer attention
• Water temperature — cold water should be stored and supplied below 20°C; hot water should be stored at 60°C and distributed at 50°C within one minute at outlets
• Stagnation risk — little-used outlets such as a spare bathroom tap or garden tap can allow water to sit stagnant and warm. These need to be flushed regularly
• Showerheads — scale and debris inside showerheads provide a breeding environment. They should be cleaned and descaled regularly
• Pipework — dead legs, poorly insulated pipes, and pipes running near heat sources all increase risk
• Water age — a property that has been empty for an extended period needs the system to be flushed before a new tenant moves in

Self-assessment in practice

For a straightforward house or flat with a combi boiler, no storage tanks, and normal hot and cold outlets, a self-assessment involves:

1. Identifying the water system type — combi boiler, storage tank, unvented cylinder
2. Checking whether any outlets are rarely used — spare bathrooms, garden taps, outside taps
3. Noting the condition of showerheads and when they were last cleaned
4. Checking pipework for any known dead legs or poor insulation near heat sources
5. Confirming hot water reaches adequate temperature at the tap within one minute
6. Recording all of the above in writing with the date of assessment

When to use a professional

A professional risk assessor is advisable — and in some cases necessary — when:

• The property has a cold water storage tank (header tank in the loft)
• The property has a complex water system, multiple storage vessels, or unusual pipework
• The property has been empty for an extended period and the system has not been properly recommissioned
• The property is an HMO or houses multiple tenants sharing water outlets
• A previous assessment identified issues that required remediation

Record keeping — what you must document

The assessment must be written down and retained. Your record should include:

• Date of assessment
• Property address
• Water system description
• Risk level identified
• Any actions taken or recommended
• Name of person who carried out the assessment
• Date for next review

Keep this record for the life of the tenancy and beyond. If a tenant were ever to contract Legionnaires' disease, your records would be central to any investigation.

How often must the assessment be reviewed?

Review when there is reason to believe it may no longer be valid — a change in use of the property, significant plumbing work, a long void period, or a change in tenant. As a general rule, reviewing every two years is good practice even if nothing has changed.

Add your Legionella assessment date to the Compliance Deadline Tracker — it will alert you when a review is due.

What to tell tenants

The HSE recommends providing tenants with brief information about Legionella precautions at the start of the tenancy:

• Flush outlets that have not been used for a week or more before use
• Do not adjust the temperature of water heaters
• Report any discolouration of water, scale build-up, or concerns about the water system
• Clean and descale showerheads periodically

Penalties for non-compliance

There is no automatic fixed penalty for a missing Legionella assessment. However, if a tenant contracts Legionnaires' disease and no assessment was carried out, a landlord could face:

• Prosecution under the Health and Safety at Work Act 1974
• Unlimited fines
• A civil claim from the tenant

A self-assessment costs nothing. A professional assessment for a higher-risk property typically costs £100–£200. The potential liability for not doing it is unlimited.