Quick answer
Landlords have a legal duty to assess and control the risk of legionella, but there is no single legal “certificate”. A written risk assessment with simple control measures is the normal way to show you have met the duty. HMOs get extra attention because of stored water, empty rooms and little-used outlets.
Legionella bacteria can grow in water systems that are stored warm or rarely used, and shared houses often have both. Landlords have a duty to assess and control the risk, although there is no single legal certificate to display. The Health and Safety Executive (HSE) publishes guidance specifically for landlords.
What the duty is
Under health and safety law, landlords must identify and assess sources of risk in the water system and put sensible controls in place. For most domestic-type systems the risk is low and controls are simple, but the assessment should be recorded. Councils often ask for a copy with an HMO licence application.
Why HMOs get more attention
- Empty rooms: water stagnates in outlets that are not used between tenants.
- Stored water: hot water cylinders and cold water tanks need correct temperatures and condition.
- Shower heads and hoses: they can harbour bacteria if not cleaned and descaled.
- More occupants: more people are exposed if something goes wrong.
What an assessment includes
A competent assessor reviews the water system, the age and condition of tanks and cylinders, temperatures, pipework dead legs and outlets. They then give a written report with practical control measures. Typical recommendations include flushing little-used outlets weekly, keeping hot water at 60°C or above at the cylinder and cold water below 20°C, descaling shower heads and recording what has been done. See our legionella risk assessments for London HMOs.
Does water need testing?
Routine sampling is not required in most domestic-type systems. The risk assessment sets out whether any monitoring is needed, so follow its advice rather than testing by default.
How often to review the assessment
Review it when the system changes, when the use of the property changes and periodically, commonly every two years. After a long void period, flush all outlets before new tenants move in.
Simple actions between assessments
- Flush any outlet that has not been used for a week.
- Keep a log with dates and initials.
- Clean and descale shower heads regularly.
- Tell tenants not to turn the water heating off for long periods.
Frequently asked questions
Is a combi boiler lower risk?
Systems without stored hot water are generally lower risk, but outlets still need assessing and flushing.
Who is responsible during a void period?
The landlord. Flush the outlets regularly while the room is empty.
Do I need a legionella certificate to get a licence?
Councils usually ask for evidence that the risk has been assessed. A current written risk assessment is the usual proof.
Sources and further reading
Related guides
- HMO landlord certificates checklist
- HMO fire risk assessment requirements
- HMO licence renewal checklist
Need this arranged across one or several properties? Request a written quote or call 07707 999369.
This guide is general information for landlords in England, not legal advice. Councils set their own HMO licence conditions, so check your borough’s requirements before you apply or renew.