Legionella risk assessments for landlords

What is a legionella risk assessment?

A legionella risk assessment identifies the risk of Legionella bacteria growing and spreading in a property's water systems. Legionella causes Legionnaires' disease, a potentially fatal form of pneumonia, and is contracted by inhaling contaminated water droplets.

Is it a legal requirement?

Yes. Under the Health and Safety at Work etc. Act 1974 and the L8 Approved Code of Practice (ACOP), all landlords have a duty to assess and control the risk of legionella in their rental properties.

There is no specific standalone fine for not having a legionella risk assessment. However, if a tenant contracts Legionnaires' disease and you cannot demonstrate that you assessed and managed the risk, you could face prosecution under health and safety law. Penalties can include an unlimited fine and imprisonment.

Does it need to be done by a professional?

No. For simple domestic properties (a house or flat with a standard hot and cold water system, a combi boiler or stored hot water, and no complex water features), the landlord can carry out the risk assessment themselves using the HSE's free guidance.

However, for more complex systems (large HMOs, properties with water storage tanks, cooling towers, or spa pools), a professional assessment is strongly recommended.

What does the assessment involve?

A basic legionella risk assessment covers:

• Water system layout: How water enters the property, how it's stored, heated, and distributed
• Water temperature: Is hot water stored and distributed at 60°C or above? Is cold water below 20°C?
• Stagnant water: Are there any dead legs (unused pipe runs), infrequently used outlets, or storage tanks?
• System condition: Is there scale, corrosion, sediment, or biofilm?
• Vulnerable occupants: Are the tenants elderly, immunocompromised, or otherwise at higher risk?

Key risk factors

Legionella thrives in specific conditions:

• Water temperature between 20°C and 45°C (the danger zone)
• Stagnant water in unused pipes, tanks, or outlets
• Scale, rust, and sediment that provide nutrients for bacteria
• Complex water systems with long pipe runs and multiple outlets

What you should do

1. Assess the risk. For simple properties, use the HSE guidance to carry out a self-assessment. For complex systems, hire a professional.
2. Set hot water above 60°C. The hot water cylinder thermostat should be set to at least 60°C. Water should reach taps at 50°C within one minute.
3. Flush unused outlets. If a property is vacant between tenancies, run all taps, showers, and other outlets for at least 2 minutes before the new tenant moves in.
4. Remove dead legs. If there are unused pipe runs (e.g. from a removed appliance), have them capped off as close to the main pipework as possible.
5. Clean showerheads. Showerheads and hoses should be descaled and cleaned regularly (at least quarterly).
6. Review every 2 years. Or sooner if circumstances change (e.g. the water system is modified, the property is extended, or vulnerable tenants move in).

Common mistakes

• Assuming it doesn't apply to simple properties. It does. Every rental property needs at least a basic assessment.
• Not reviewing the assessment. A one-off assessment is not enough. Review every 2 years or when circumstances change.
• Ignoring vacant periods. Stagnant water during void periods is one of the biggest risk factors. Always flush the system before a new tenant moves in.
• Setting hot water too low. Some landlords lower the thermostat to save energy. Below 60°C increases legionella risk significantly.

How LetShield helps

LetShield tracks your legionella risk assessment date and sends reminders when it's due for review. The compliance dashboard shows a clear status so you know which properties have a current assessment and which need attention.