Legionella Risk Assessment for Landlords: Do You Need One?

Legionella risk assessments are one of the less well-known landlord obligations. Many landlords are either unaware they need one or unsure what it involves. This guide explains the legal position, what an assessment covers, how much it costs, and the simple control measures that keep your tenants safe and your compliance on track.

What Is Legionella?

Legionella is a type of bacteria found naturally in freshwater sources such as rivers and lakes. It becomes a health risk when it multiplies in man-made water systems — including domestic plumbing, hot water tanks, showers, and air conditioning units — and is then inhaled as tiny water droplets (aerosols).

Infection with legionella bacteria can cause Legionnaires' disease, a serious and potentially fatal form of pneumonia. It can also cause the less severe Pontiac fever. People most at risk include those over 45, smokers, heavy drinkers, and anyone with a weakened immune system.

Legionella thrives in water temperatures between 20°C and 45°C, with the greatest risk between 25°C and 42°C. Below 20°C the bacteria go dormant; above 60°C they are killed. This temperature range is the key to understanding both the risk and the control measures.

The Legal Position for Landlords

Landlord obligations regarding legionella come primarily from the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 (COSHH). The Health and Safety Executive (HSE) has issued specific guidance for landlords in its document "Legionnaires' disease: A brief guide for dutyholders" (INDG458).

What the HSE Says

The HSE's position is clear: landlords are responsible for the health and safety of their tenants in relation to the water systems in their properties. This means you must:

• Assess the risk of legionella exposure from your property's water systems
• Identify and implement measures to control any risks identified
• Keep records of any precautions taken
• Review the assessment periodically and whenever changes are made to the water system

Importantly, the HSE acknowledges that the risk from most domestic systems is low. A simple assessment is usually sufficient, and in many cases landlords can carry out the assessment themselves without specialist help.

Is It a Legal Requirement?

Yes. The duty to assess and control the risk of legionella applies to all landlords, whether you let a single house or manage a large portfolio. It's not optional, and there is no exemption for small landlords or particular property types.

That said, the HSE recognises that the level of assessment needed depends on the risk. For a typical domestic property with a straightforward hot and cold water system, the assessment can be simple and brief. Complex systems (large hot water storage tanks, multiple outlets, rarely used shower rooms) warrant more detailed assessment.

When Is an Assessment Needed?

You should carry out a legionella risk assessment:

• Before letting a property for the first time: As part of your pre-tenancy compliance checks
• Between tenancies: Particularly if the property has been empty for a period (stagnant water increases legionella risk)
• After changes to the water system: Installing a new boiler, adding a bathroom, or changing the plumbing layout
• Periodically during a tenancy: The HSE recommends reviewing the assessment at least every two years, or sooner if circumstances change

There is no fixed legal timeframe for reassessment, but two years is the commonly accepted standard. Many landlords align it with other compliance renewals to keep track more easily.

What Does an Assessment Involve?

For a typical domestic rental property, a legionella risk assessment covers the following areas:

Water System Overview

• Type of hot water system (combi boiler, system boiler with hot water tank, immersion heater)
• Cold water supply (mains-fed or from a storage tank)
• Number and location of outlets (taps, showers, baths)
• Any outlets that are rarely used
• Condition and age of pipework

Temperature Checks

• Hot water temperature at the boiler or tank (should be stored at 60°C or above)
• Hot water temperature at outlets (should reach 50°C within one minute of running the tap)
• Cold water temperature at outlets (should be below 20°C within two minutes of running the tap)

Risk Factors

• Stagnant water in dead legs (sections of pipework that no longer serve an outlet)
• Water storage tanks — are they covered, insulated, and free from contamination?
• Showerheads and hoses — can they create aerosols from warm, stagnant water?
• Rarely used outlets — any taps or showers that go unused for more than a week
• Cold water storage tanks in warm locations (such as airing cupboards or loft spaces without insulation)

Vulnerable Occupants

The assessment should consider whether any occupants are at higher risk of legionella infection. While you may not always know your tenants' health status, properties let to older adults or those known to have compromised immune systems may warrant additional precautions.

DIY vs Professional Assessment

The HSE does not require you to use a professional assessor for straightforward domestic properties. If you have a reasonable understanding of your property's water system, you can carry out the assessment yourself using the HSE's guidance.

When You Can Do It Yourself

• Standard domestic property with a combi boiler (no stored hot water)
• Mains-fed cold water (no cold water storage tank)
• All outlets used regularly
• Simple plumbing layout with no dead legs or complex pipework

In these cases, the risk is generally low. A combi boiler heats water on demand and doesn't store it, removing one of the main risk factors. Mains-fed cold water is constantly refreshed, reducing the chance of stagnation.

When to Use a Professional

• Properties with hot water storage tanks (particularly older, larger tanks)
• Properties with cold water storage tanks (common in older buildings)
• HMOs with complex plumbing serving multiple bathrooms and kitchens
• Properties with rarely used outlets or areas
• Properties where you're unsure about the plumbing layout
• If you simply want the reassurance of a professional assessment and documented report

Cost of a Professional Assessment

A professional legionella risk assessment for a standard domestic rental property typically costs between £50 and £150. The price depends on:

• Property size and complexity
• Number of water outlets
• Type of water system
• Location (prices vary regionally)
• Whether temperature monitoring is included

For HMOs or larger properties, costs can be higher — typically £200 to £400. Some providers offer discounted rates for landlords with multiple properties.

Given the potential liability if a tenant contracts Legionnaires' disease and you cannot demonstrate that you assessed and controlled the risk, this is a relatively modest cost.

Simple Control Measures

For most domestic rental properties, controlling legionella risk involves straightforward measures that don't require specialist equipment or significant expense.

Temperature Management

• Hot water storage: If you have a hot water tank, ensure the thermostat is set to at least 60°C. This kills legionella bacteria in stored water.
• Thermostatic mixing valves (TMVs): Where water is stored at 60°C, TMVs at outlets can blend it down to a safe temperature (typically 43-46°C) to prevent scalding, while maintaining the storage temperature needed to control legionella.
• Cold water: Ensure cold water pipes are insulated in warm areas to keep the water below 20°C.

Flushing Rarely Used Outlets

Any tap, shower, or other outlet that is not used for a week or more should be flushed by running both hot and cold water for at least two minutes. This clears any stagnant water where bacteria could have multiplied.

This is particularly important:

• In void periods between tenancies
• In guest bedrooms or en-suites that are rarely used
• After holidays or periods when the property is unoccupied

If your tenants are away for extended periods, advise them to run all taps and showers for a few minutes when they return. Include this guidance in your tenant welcome pack or tenancy agreement.

Showerhead Cleaning

Showerheads can harbour legionella bacteria in limescale and biofilm. Recommend that tenants clean showerheads regularly by descaling them — either by soaking in a descaling solution or replacing them periodically. At property inspections, check the condition of showerheads and replace any that are heavily scaled.

Removing Dead Legs

Dead legs are sections of pipework that no longer serve an active outlet — for example, where a tap has been removed but the pipe still connects to the system. These create areas of stagnant water ideal for bacterial growth. If you identify dead legs during your assessment, have a plumber cap them off as close to the main supply as possible.

Water Tank Maintenance

If the property has a cold water storage tank (typically in the loft):

• Ensure it has a tight-fitting lid to prevent contamination from debris, insects, or animals
• Check that it's properly insulated to keep water cool
• Ensure the ball valve is working correctly so water is refreshed regularly
• Consider whether the tank is still necessary — many properties can be converted to mains-fed cold water, eliminating the storage tank risk entirely

Tenant Communication

While you are responsible for the risk assessment and the water system's infrastructure, tenants play a role in day-to-day control measures. Inform your tenants about:

• Not adjusting the hot water thermostat below the set temperature
• Running rarely used taps and showers weekly
• Cleaning showerheads regularly
• Reporting any issues with water temperature (hot water not reaching adequate temperature, cold water running warm)
• Letting you know if they plan to be away for more than two weeks

You don't need to alarm tenants — the risk in most domestic properties is low. A simple information sheet included with your tenancy documents is sufficient.

Documentation and Record Keeping

As with all compliance obligations, documentation is key. Keep records of:

• The risk assessment itself: Date, who carried it out (you or a professional), findings, and risk rating
• Control measures implemented: What you did to address any risks identified (thermostat settings, dead leg removal, tank maintenance)
• Temperature checks: If you carry out periodic temperature monitoring, record the results
• Tenant communication: Evidence that you informed tenants about legionella control measures
• Review dates: When the assessment was last reviewed and when the next review is due
• Any changes to the water system: New boiler installations, plumbing modifications, or additions

Store these records alongside your other property compliance documents. If you use a platform like HouseFile, you can keep everything in one place with reminders for when reviews are due. For a full overview of what records landlords should maintain, see our landlord compliance checklist.

Liability and What Can Go Wrong

If a tenant contracts Legionnaires' disease and you have not carried out a risk assessment or implemented reasonable control measures, you face potential liability on several fronts:

• HSE enforcement: The Health and Safety Executive can investigate and prosecute. Penalties include unlimited fines and imprisonment for serious breaches.
• Civil claims: A tenant who becomes seriously ill can pursue a personal injury claim. Legionnaires' disease can require hospitalisation, cause long-term health effects, and in severe cases can be fatal. Damages in such cases can be substantial.
• Insurance implications: Your landlord insurance may not cover claims related to legionella if you cannot demonstrate that you took reasonable steps to assess and manage the risk.
• Local authority action: Environmental health officers can take enforcement action under housing legislation if they identify a legionella risk during an inspection.

The good news is that demonstrating compliance is straightforward. A documented risk assessment, evidence of basic control measures, and periodic reviews are usually all that's needed. For tips on proving delivery of safety documents to tenants, see our guide on proving tenants received documents.

Legionella and Other Compliance Obligations

Legionella risk assessment sits alongside your other compliance duties. It's helpful to consider it as part of your overall property safety regime rather than an isolated task. Your annual compliance cycle might include:

• Gas safety certificate (annual) — see our guide on gas safety certificates for landlords
• EICR (every five years)
• Smoke and CO alarm checks (at each tenancy start)
• Legionella risk assessment review (every two years)
• Fire risk assessment (annual review for HMOs)
• EPC (every ten years)

Keeping all these obligations tracked and documented ensures nothing falls through the cracks. Our landlord responsibilities checklist for 2026 provides a comprehensive overview of all current requirements.

Key Takeaways

• Legionella risk assessment is a legal requirement for all landlords, not optional
• For most standard domestic properties with combi boilers and mains-fed water, the risk is low and the assessment is simple
• Professional assessments cost £50-£150 and are worthwhile for peace of mind and a documented record
• Basic control measures — correct temperatures, regular flushing, showerhead cleaning — are easy to implement
• Document your assessment and control measures, and review at least every two years
• The consequences of not having an assessment in place are far more costly than the assessment itself

Legionella risk assessment is one of those landlord obligations that sounds more complicated than it is. For most properties, it takes less than an hour, costs very little, and gives you documented evidence that you're meeting your duty of care. It's a small step that protects both your tenants and yourself.