HSE says landlords must assess and control legionella risk in domestic hot and cold water, but a simple assessment is usually enough. Temperature is the main control, and combi boilers without storage lower the risk.
In this guide
A landlord’s duties around a hot water system go beyond the annual gas safety check. The Health and Safety Executive (HSE) says that landlords have a legal duty to assess and control the risk of legionella bacteria in the water systems of homes they let. This guide summarises HSE’s page on legionella and landlords’ responsibilities, last updated on 30 September 2024. HSE regulates in Great Britain. This is general information, not property-specific advice.
What the law requires of a landlord
HSE describes Legionnaires’ disease as a potentially fatal form of pneumonia caused by inhaling small droplets of water contaminated with legionella, and says all man-made hot and cold water systems are likely to provide an environment where the bacteria can grow. It defines a landlord as anyone who rents out a property they own under a lease or licence shorter than seven years, including local authorities, housing associations, private landlords and housing co-operatives, and says the duty can apply even to letting a room within the owner’s own home.
The legal basis is the Health and Safety at Work etc. Act 1974: section 3(2) applies a duty of care to tenants, and under section 53 landlords are treated as self-employed. The Control of Substances Hazardous to Health Regulations (COSHH) cover biological agents such as legionella, and HSE’s Approved Code of Practice L8 gives guidance. Gas safety obligations are a separate regime, summarised in the guide to landlord gas safety certificates.
A proportionate risk assessment
HSE says the duty is to assess the risk from exposure to legionella, but that for domestic rental properties this does not require an in-depth, detailed assessment. It describes a typical low-risk home as one where daily water use turns over the whole system, cold water comes straight from a mains supply with no storage tank, and hot water comes from instantaneous heaters or low-volume water heaters supplying outlets at 50°C. HSE adds that the risk is lowered further where instantaneous water heaters, such as combi boilers and electric showers, are installed, because there is no water storage. A simple assessment may show there are no real risks and no further action is needed, but it should be reviewed if anything in the system changes.
Temperature and simple controls
For most domestic systems, HSE says temperature is the most reliable control: keep the hot water hot, the cold water cold and keep it moving. The practical measures it lists are:
- flushing the system before letting the property;
- avoiding debris entering the system, for example by fitting tight-fitting lids to cold water tanks;
- setting the hot water cylinder, also called the calorifier, so that water is stored at 60°C; and
- removing any redundant pipework.
These are storage and distribution temperatures, not a recommendation to expose skin to water at those temperatures. Scald prevention, including suitable mixing controls where needed, must be designed alongside Legionella control by a competent person.
The way cylinders are specified and replaced is covered in the guide to vented and unvented hot water cylinders.
What tenants should be told
HSE says tenants should be advised of the control measures that must be maintained. They should not adjust the temperature setting on the calorifier, should regularly clean showerheads, and should tell the landlord if hot water is not heating properly or there are other problems. HSE explains that showers create droplets (aerosols) that could be inhaled, and that instantaneous electric showers pose less risk because they are generally cold-water fed and heat only small volumes during use. The guide to boiler problems in a rented home covers who arranges repairs.
Empty properties
HSE says water must not be allowed to stagnate, so properties left vacant for long periods, such as student accommodation over the summer, need careful management. As a general principle, it says outlets on hot and cold systems should be used at least once a week to maintain a degree of flow, and a suitable flushing regime or draining the system can be considered if the property will be empty for long.
Testing, records and liability
HSE states that testing or sampling for legionella is not usually required for domestic hot and cold water systems and is needed only in very specific circumstances. Health and safety law does not require landlords to obtain a “legionella test certificate”, and testing should not be confused with temperature monitoring, which HSE calls a reliable way of confirming that a system is under control. Landlords are not necessarily required to record the assessment, which is a statutory duty only for employers with five or more employees, although HSE says keeping a record may be wise. The assessment should be reviewed periodically, and checks can be made during mandatory visits such as gas safety checks.
HSE and local authority inspectors do not proactively inspect domestic premises or ask for evidence of an assessment. However, if a tenant contracted Legionnaires’ disease from the water system in their home, HSE says the landlord may be liable to prosecution under the 1974 Act and would have to show a court that the legal duty had been fulfilled.
FAQs
Do I need a legionella test certificate for a rented home?
No. HSE says health and safety law does not require landlords to obtain or produce one, and testing is not usually required for domestic systems.
Does a combi boiler lower the risk?
HSE says the risk is further lowered where instantaneous water heaters such as combi boilers are installed, because there is no water storage.
The bottom line
In Great Britain a landlord must assess and control legionella risk in the hot and cold water of a let home, but HSE accepts a simple, proportionate assessment: keep hot water hot at the cylinder, cold water cold, keep it moving, flush before letting and tell tenants to leave the temperature setting alone and clean showerheads. Combi boilers and electric showers lower the risk because they store no hot water. Testing is not usually needed, but failing to manage the risk can expose a landlord to prosecution if a tenant falls ill. This is general information, not personalised advice.
Sources
This guide draws on the following primary sources, current as of 9 October 2026:
- Health and Safety Executive, Legionella and landlords’ responsibilities, updated 30 September 2024 (hse.gov.uk)
- Health and Safety Executive, Legionella and Legionnaires’ disease (hse.gov.uk)
Related guides
Landlord gas safety certificates
Vented and unvented cylinders
Boiler problems in a rented home
Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation; always confirm the details with a Gas Safe registered engineer.