Do HMO's need a Legionella Risk Assessment?

If you manage or own a House in Multiple Occupation (HMO), you may be wondering whether a Legionella risk assessment is legally required and if so, what’s actually involved.

The short answer is: yes, in most cases HMOs do require a Legionella risk assessment.

The level of assessment and ongoing control measures will depend on the size, layout and water systems within the property.

Let’s break it down clearly.

What Is Legionella and Why Does It Matter?

Legionella bacteria can develop in man-made water systems such as:

• Hot and cold water systems

• Water storage tanks

• Shower heads and hoses

• Dead legs in pipework

• Spa baths or other specialist systems

  
  

If inhaled through water droplets (for example, from a shower), Legionella can cause Legionnaires’ disease, a potentially serious form of pneumonia.

HMOs typically house multiple unrelated tenants sharing facilities, the risk profile is often higher than a single private dwelling.

What Does the Law Say?

Under UK law, landlords have a legal duty to assess and control the risk of exposure to Legionella bacteria.

This duty comes from:

• Health and Safety at Work etc. Act 1974

• Control of Substances Hazardous to Health Regulations (COSHH)

• HSE Approved Code of Practice L8 (ACOP L8)

• HSG274 Part 2 (Technical guidance)

  
  

The HSE makes it clear:

Landlords must assess and control the risk of Legionella in their rental properties.

This applies to:

• Private landlords

• Letting agents

• Housing associations

• HMO operators

There is no exemption for small HMOs.

Are HMOs Treated Differently?

HMOs are often considered higher risk than standard single-family lets because:

• Multiple occupants use shared showers and taps

• There may be larger or more complex water systems

• Some HMOs have cold water storage tanks

• Turnover of tenants may mean systems are unused for periods

• Licensing requirements increase scrutiny

If your HMO is licensed, your local authority may specifically request evidence of Legionella control as part of inspections.

Do You Legally Need a “Formal” Risk Assessment?

The law requires you to carry out a risk assessment — but it does not always require it to be done by an external contractor.

However, in practice:

• Small, modern HMOs with combi boilers may be lower risk

• Larger HMOs with tanks, calorifiers or complex pipework are higher risk

• If you are unsure, you are expected to seek competent advice

For most HMOs, particularly licensed ones, a documented professional Legionella risk assessment is strongly recommended.

Why?

Because if there were ever an investigation, you must prove that:

• The risk has been assessed

• Control measures are in place

• The system is being monitored

Without documentation, that becomes very difficult.

What Does an HMO Legionella Risk Assessment Involve?

A typical professional assessment will include:

• Inspection of the hot and cold water systems

• Identification of water storage tanks

• Review of pipework and potential dead legs

• Temperature testing

• Identification of high-risk areas

• A written report outlining findings

• Clear recommendations for control measures

Reports are usually carried out in line with HSE ACOP L8 and BS8580 guidance.

What Happens If You Don’t Have One?

Failure to assess and control Legionella risk can result in:

• Enforcement action from the HSE or local authority

• Improvement or prohibition notices

• Fines

• Prosecution in serious cases

  
  

More commonly, landlords run into issues when:

• Applying for or renewing HMO licences

• Dealing with insurance queries

• Undergoing inspections

• Selling or refinancing the property

In many cases, landlords only seek an assessment urgently when they realise it is required for compliance.

Ongoing Responsibilities for HMO Landlords

A risk assessment is not a one-off tick box.

Landlords must also ensure:

• Hot water is stored at 60°C and distributed at 50°C+

• Cold water is below 20°C

• Shower heads are cleaned and descaled regularly

• Water tanks are maintained and insulated

• Records are kept

The frequency of review depends on the system and level of risk, but assessments should be reviewed periodically or when there are significant changes to the system.

When Is an HMO Considered Low Risk?

An HMO may be considered lower risk if it:

• Has a modern combi boiler (no stored water)

• Has no cold water storage tanks

• Has minimal pipework

• Is regularly occupied

However, even in lower-risk properties, the landlord must still demonstrate that a risk assessment has been carried out.

“Low risk” does not mean “no responsibility.”

Should You Get a Professional Assessment?

While some small landlords complete basic assessments themselves, HMOs — particularly licensed or larger properties — are generally better suited to professional assessments.

A professional report provides:

• Clear documentation

• Compliance reassurance

• Evidence for insurers or local authorities

• Practical, realistic advice

• Support if questioned

For many landlords, that peace of mind is worth it.

If you operate or manage an HMO, you have a legal duty to assess and control the risk of Legionella. In most cases, particularly for licensed or multi-storey HMOs, a documented professional Legionella risk assessment is strongly recommended.

Compliance isn’t just about ticking a box — it’s about protecting tenants, protecting yourself legally, and ensuring your property meets regulatory standards.