Legionella Risk Assessment for Landlords: What You Actually Need to Do

Legionella attracts more confusion, and more overpriced services, than almost any other part of landlord compliance. Some landlords are told they need an expensive yearly "legionella certificate". Others have never heard of it. The truth sits in between.

The legal position

Landlords have a duty under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health (COSHH) Regulations to assess and control the risk of exposure to legionella for their tenants. HSE's approved code of practice, ACOP L8, sets out how. There is no legal requirement for a "legionella certificate", and water testing is not usually needed for homes.

What you do need is a risk assessment: a sensible look at the water system and any simple control measures. The law does not require most landlords to write it down (that duty applies to employers with five or more staff), but keeping a dated record is strongly advisable. It is your evidence if a tenant ever falls ill.

What makes legionella a risk?

Legionella bacteria multiply in water between about 20°C and 45°C, especially where water sits still and where there is sludge, scale or biofilm. People are infected by breathing in tiny contaminated droplets, for example from a shower. The higher-risk features in rented homes are:

• Stored water, such as cold water tanks in lofts and hot water cylinders
• Dead legs: pipework to removed or rarely used outlets
• Showers, especially little-used ones
• Homes left empty between tenancies
• Hot water stored below 60°C

A modern flat with a combi boiler and no stored water is usually low risk. An older house with a loft tank, a cylinder and a little-used en-suite needs more thought.

A simple risk assessment checklist

For a typical single let, your assessment should note:

1. System type: combi or stored hot water? Cold water tank or mains-fed?
2. Temperatures: is stored hot water kept at 60°C or above? Does hot water reach 50°C at outlets within one minute? Is cold water below 20°C after running the tap for two minutes?
3. Tanks: is the cold water tank covered, insulated and free of debris?
4. Little-used outlets: any showers, taps or rooms not in regular use?
5. Dead legs: any pipework that is no longer needed and can be removed?
6. Empty periods: will the home be empty for a while? If so, plan to flush outlets before new tenants move in.
7. Tenants at higher risk: people over 45, smokers, heavy drinkers, and people with chronic illness (such as respiratory or kidney disease, or diabetes) or a weakened immune system.
8. Tenant information: have tenants been told to run little-used outlets, leave boiler settings as set, and report problems?
9. Review: when will you look again, for example at a change of tenant or after any change to the water system?

Write it down, date it, and keep it with the property's other certificates.

When to call in a professional

HSE says most landlords can assess the risk themselves and do not need professional training or accreditation. Consider a professional if:

• The property is an HMO or has shared water systems
• There are large stored water systems
• You have found temperatures you cannot control or a contaminated tank
• Your HMO licence or insurer asks for a professional assessment

How CertBox helps

CertBox's legionella risk assessment gives contractors who carry out assessments a structured form, based on ACOP L8 and HSE's technical guidance, to complete on site:

• Prompts for the key checks above, so nothing is missed.
• A professional PDF the landlord can store against the property in their landlord account.
• Kept alongside the gas, electrical and fire certificates, so a council or tenant can see the full picture in one place.
• A QR code, so anyone it is shared with can confirm it is genuine.

Frequently asked questions

Do landlords legally need a legionella test?

No. The legal duty is to assess and control the risk. Water sampling is only expected in specific higher-risk situations.

How often should a legionella risk assessment be reviewed?

There is no fixed legal interval. Review it whenever something significant changes, such as the water system or the people living there, and from time to time otherwise.

Can a letting agent do the risk assessment?

Yes, if they are competent and your management agreement says they will do it. If the agreement does not make that clear, responsibility stays with the landlord. Either way, ask to see a copy.

Is legionella a risk in a flat with a combi boiler?

Usually low, because there is no stored hot water. You should still record that assessment and note any little-used outlets.

Sources

Checked against these on 2026-10-20.

• HSE: Legionella and landlords’ responsibilities
• HSE: Hot and cold water systems
• HSE: What is legionnaires’ disease
• HSE: ACOP L8, Legionnaires’ disease
• HSE: Landlords FAQ (gas)

Corrected and updated 2026-10-20. This article is for general guidance only and does not constitute legal or professional advice. Always refer to the relevant standards and consult qualified professionals for definitive requirements.